Home Diseases Covid-19: contagion, symptoms and treatment

Covid-19: contagion, symptoms and treatment

by Josephine Andrews
Published: Last Updated on 339 views


Covid-19 is the name of a disease caused by the novel coronavirus Sars-CoV-2. It mainly affects the airways and can cause severe pneumonia. But damage to other organs, thrombosis and dangerous sepsis are also possible serious complications. In December 2019, the first cases of Covid-19 from China became known. The disease is now widespread worldwide. How is the pathogen transmitted? What symptoms does Covid-19 cause? What does the treatment look like? read more!

ICD codes for this disease:

ICD codes are internationally valid codes for medical diagnoses. They can be found, for example, in doctor’s letters or on certificates of incapacity for work.


quick overview

  • What is Covid-19? a multi-organ disease, especially of the lungs, caused by corona viruses
  • Pathogen : the Sars-CoV-2 type of coronavirus
  • Transmission route: mainly via droplet infections and aerosols
  • Symptoms : including cough , fever, runny nose , disturbance of the sense of smell and/or taste, pneumonia
  • Risk groups : especially old people, the chronically ill, smokers, the overweight
  • Distribution : Originated in China, since spreading worldwide coronavirus
  • Therapy : relief of symptoms; if necessary, oxygen supply, ventilation; in certain patients remdesivir, dexamethasone or treatment as part of studies
  • Prevent : Mouth and nose cover, keep your distance (at least 1.5 meters), hygiene measures, ventilation, quarantine for infected people, avoid mass gatherings and risk areas

What is Covid-19, what is the corona virus?

Covid-19 is an infectious disease caused by the novel coronavirus Sars-CoV-2. These primarily affect the respiratory tract. In the lungs , the pathogens can sometimes cause severe pneumonia. If breathing fails as a result , Covid-19 can be fatal.

However, the pathogen can also affect other organs, such as nerves, heart , blood vessels, liver and kidneys. These organs are equipped with a particularly large number of docking points (receptors) for the hormone ACE2. The virus uses this to invade the body’s cells

In the course of the disease, thrombosis often forms, which can migrate to the lungs or brain. An excessive immune response of the body to the virus, a so-called sepsis, which is life-threatening, is also feared. During its course, various organs can fail.

The name Covid -19 is the abbreviation of the English term “ Corona-Virus isease  . The number 19 stands for the year in which the pathogen was officially discovered: 2019.

New variants (mutations)

The virus developed numerous genetic variants in the two years of the pandemic. The vast majority of such mutations are insignificant. However, some emerging virus variants are a cause for concern.

These are, for example, those that can spread faster or escape the immune system better – for example the youngest representatives of the delta or now currently the omicron variant.

Further information on the newly circulating virus variants can be found here .

Classification of the infection

Doctors divide Covid-19 patients into different degrees of severity depending on the course of the disease:

  • Light and uncomplicated: no inflammation of the lungs (pneumonia)
  • Moderate : mild pneumonia
  • Severe : Pneumonia with fever and bilateral pulmonary infiltrates (tissue compaction visible on X-ray) and either
    • Respiratory rate over 30 per minute or
    • severe shortness of breath or
    • Oxygen saturation below 90 percent in room air
  • Critical : acute lung failure, excessive immune response (hyperinflammation) with the clinical picture of sepsis or septic shock with multi-organ failure

About 80 percent of Covid-19 diseases are mild to moderate. However, they too can become severely ill and take a long time to fully recover.

In the course of the disease, clinical deterioration occurs in about 14 percent of patients. They typically develop shortness of breath and a lack of oxygen in the blood seven to ten days after the onset of symptoms . In about 7 percent of those who are ill, Covid-19 takes a critical course, so that they have to be treated in hospital.

The World Health Organization reports that mild cases have an average course of illness of two weeks. In severe cases, the Covid-19 illness lasts about three to six weeks.

About 22 percent of the Covid-19 patients in Germany who were treated in intensive care die of the disease (as of November 2020).

Where does the corona virus come from?

According to the current state of knowledge, the new Sars viruses originate in China. The epicenter of the outbreak was the city of Wuhan. Here, in December 2019, there were a number of cases of illness for the first time. They primarily affected people who had been to a meat and fish market where wild animals were also sold.

According to the current situation, the virus jumped from a wild animal to humans. Experts assume that the pathogen originally came from bat populations. Experts have detected very closely related Sars-CoV-2 viruses in these animals.

Humans eventually became infected via another intermediate host, possibly a pangolin. SARS (civets) and MERS (dromedaries) also originated in wild animals – diseases caused by other types of coronavirus.

Coronavirus spread

Sars-CoV-2 “jumps” easily from person to person. In addition, infected people who are symptom-free and those who are slightly ill can infect other people. As a result, the virus has spread across the globe.

The World Health Organization has therefore declared the 2019/2020 outbreak a pandemic. Experts now assume that Sars-CoV-2 will become endemic – which means that it will probably circulate in the population worldwide in the long term and repeatedly cause localized outbreaks.

Corona virus: Current situation in Germany

The course of infection changes rapidly. The current numbers about the corona virus and infected people in Germany and worldwide can be found in our article ” Coronavirus: current case numbers “.

In addition, you will find background information about the virus, the effects of the corona virus and the current state of research in our special topic ” Everything about the coronavirus infection Covid-19 “.

In April 2020, the average age of newly infected people in Germany was 52. The proportion of patients who had to be treated in hospital was 20 percent at the time. After a temporary drop in the average age of those infected to 32, it is now 42. The hospitalization rate has fallen to six percent (as of November 2020).

Older patients who are infected with the novel coronavirus have to be hospitalized more often than younger patients: the average age for inpatient treatment is 72 years. 86 percent of deaths from Covid-19 affected people aged 70 or older.

Women and men are currently equally affected. However, men are more likely to become seriously ill with Covid-19 and have an overall higher risk of death.

Coronavirus: Symptoms of Covid-19

How the lung disease Covid-19 manifests itself varies from patient to patient. Some infected people have no symptoms at all, others only have a slight cough or runny nose. In some cases, the disease is severe: sufferers get a pronounced pneumonia. In this case, the coronavirus infection can be fatal.

The most common symptoms of coronavirus infection include:

  • cough
  • fever
  • sniffle
  • Disturbance of the sense of smell and/or taste
  • inflammation of the lungs (pneumonia)

The virus primarily affects the respiratory tract. Those affected often develop flu-like symptoms at first. You feel ill and exhausted, get (usually rather moderate) fever and a dry cough. Almost every third person also suffers from a cold.

In severe cases, pneumonia eventually develops – often during the second week of illness. Those affected primarily complain of shortness of breath, which in some cases can increase rapidly.

Shortness of breath indicates the beginning of a severe course of Covid-19! Regular measurement of oxygen saturation is then particularly important. So get medical help as soon as possible if you get bad breath!

A particular sign of coronavirus infection is the sudden loss of smell and taste. This occurs in about 21 percent of patients and often begins at the onset of the disease.

In the course of the infection, corona symptoms can also occur in the gastrointestinal tract:

Rare coronavirus symptoms include:

  • Sore Throat
  • headache and body aches
  • inflammation of the eye (conjunctivitis)
  • skin rash
  • Lymph node swelling

Possible neurological coronavirus symptoms in humans include:

  • indifference
  • absence
  • drowsiness

Especially in older patients, confusion, drowsiness or severe sleepiness are important signs of a severe course of the corona virus! Because due to previous illnesses, shortness of breath is often wrongly not perceived as a threatening symptom of Covid-19.

Differences between Covid-19 and flu

Covid-19 and the “real” flu (influenza) are often compared with each other – they sometimes cause similar symptoms and both can be difficult.

An important difference, however, is the speed at which the disease progresses: flu symptoms usually appear very quickly and violently. Within a few hours, the patients feel very ill and develop a high fever. In contrast, Covid-19 develops more slowly – the condition of the patients worsens over the course of several days.

In addition, a coronavirus infection is more often associated with a cold than the flu. The temporary loss of smell and/or taste is also an indication of Covid-19.

You can read more about the distinction in the article ” Coronavirus or flu? Those are the differences! “.

Coronavirus: treatment

Doctors treat mild to moderate Covid 19 disease symptomatically: depending on need, they prescribe fever reducers or painkillers, for example. Doctors use other medications for people who are seriously ill or who are particularly at risk. These act specifically against the viruses.

If the disease is severe, treatment usually takes place in the hospital. Under certain circumstances, intensive care measures are also necessary (eg ventilation).

Outpatient therapy – what you can do yourself

If you have minor symptoms, you can cure your illness at home . It is best to stay in a different room from members of the household who are not ill to prevent infection. Make sure you drink enough and take it easy on your body.

Talk to your family doctor , especially if you suffer from chronic diseases. These include, for example, severe obesity , high blood pressure , diabetes, chronic heart and lung diseases or a weak immune system. He will discuss the further procedure with you and tell you what you should pay particular attention to.

The state of health can deteriorate rapidly with Covid-19. Get medical help right away if you or the affected person is breathing difficult or unusually fast. Circulatory problems are also a warning signal.

Drug treatment of Covid-19

Depending on the course of the disease, doctors use different drugs for Covid-19. These alleviate the symptoms , curb a violently reacting immune system or target Sars-CoV-2 directly . Medicines are mainly used in severe cases of Covid-19. There are also special active ingredients for high-risk patients who are particularly at risk due to previous illnesses.

You can read everything you need to know about medication for Covid-19 and what you can do if you have mild Covid-19 symptoms in our article “ Corona medication ”.

measures in the hospital

In inpatient Covid-19 treatment, doctors take various general measures:

  • rather restrained fluid therapy : Too much fluid can worsen the oxygen supply in severe Covid-19 as it puts additional stress on the inflamed lungs.
  • Patient monitoring : Doctors can thus identify critical developments at an early stage.
  • Thrombosis prophylaxis to avoid blood clots
  • Consideration of concomitant diseases (comorbidities) in the treatment
  • Regular control of the inflammation parameters, kidney function , liver values , coagulation, etc. with blood tests

Those affected usually also need oxygen. If the course of the disease is very severe, treatment in the intensive care unit is necessary, if necessary with artificial ventilation. Other organs can also fail (multiple organ failure). Doctors then take specific measures to support the organs or replace failed functions (eg kidney replacement procedures).

oxygenation and ventilation

If there is not enough oxygen in the blood, doctors administer the vital gas through a thin tube on the nose (so-called oxygen nasal cannula) or through an oxygen mask. Sometimes they also use special “nasal cannulas” (high-flow nasal cannula, HFNC), through which the patient receives a particularly large amount of oxygen in a short time ( high-flow oxygen therapy ).

If that is not enough, mechanical ventilation must be used: if the condition of the Covid 19 patient allows it, the first step is non-invasive ventilation . This is done using a special ventilation mask or hood. As a rule, this only supports breathing – the patient must therefore still be able to breathe on his own to a certain extent.

In the case of fulminant lung failure (ARDS, acute respiratory distress syndrome), non-invasive ventilation is no longer sufficient. Invasive ventilation is then necessary. Doctors put the person in an artificial coma and insert a breathing tube into the lungs ( intubation ).

If that doesn’t help either, doctors can still use what is known as ECMO (extracorporeal membrane oxygenation). A special device outside the body takes over the function of the lungs.

Dismissal at Covid-19

When can patients with Covid-19 leave the clinic or isolation? That depends on how the coronavirus infection progresses.

Patients with a severe course of Covid-19 who were dependent on oxygen during therapy must be symptom-free for at least 48 hours. In addition, a corona PCR test must be negative. In addition, discharge occurs at the earliest ten days after the onset of symptoms.

People with a mild course of Covid-19 who do not need oxygen are discharged if they have been symptom-free for 48 hours. However, here, too, discharge takes place at the earliest ten days after the onset of symptoms.

Covid-19 patients with an asymptomatic course of the disease may not leave the isolation at the earliest ten days after the first detection of Sars-CoV-2.

Patients with a congenital or acquired immunodeficiency and people undergoing therapy that suppresses the immune system (eg chemotherapy ) may have prolonged excretion of infectious viral material. Here, a decision on dismissal is always made individually in each case.

Rehabilitation after coronavirus infection

Rehabilitation can be helpful, especially after a severe or even critical course of Covid-19. This can already begin on the normal ward of the hospital and after the patient has been discharged it can take place on an inpatient or outpatient basis. The main focus of rehabilitation is the restoration of lung function. Therefore, it usually takes place in pneumology clinics.

The following criteria are the prerequisite for rehabilitation after undergoing a coronavirus infection:

  • The symptoms have disappeared for at least two days.
  • Respiration and circulation are stable.
  • After the intensive care unit, the patient was returned to the normal ward.

Corona virus: contagion

The virus spread quickly in the first corona epicenter, Wuhan. Researchers discovered early on that people can also become infected from infected people who do not (yet) have any symptoms, ie are not (yet) ill with Covid-19.

Coronavirus infection routes

According to the current state of knowledge, the main transmission of corona viruses takes place via tiny droplets floating in the air (aerosols) or droplet infection . However, other routes of infection are also likely or at least possible.


It is now assumed that a large proportion of people were infected via so-called aerosols. Physicians and virologists describe the smallest virus-containing respiratory air particles as aerosols. These are smaller than five micrometers and can be transferred from the breath into the air in the room.

However, aerosols have two other problems. On the one hand, they can travel longer distances than larger droplets. On the other hand, they don’t fall to the ground as quickly as these. As a result, virus-containing aerosols accumulate in the air – which increases the risk of corona infection in closed rooms.

The transmission of the corona virus via aerosols can also take place over a distance of more than two meters.

droplet infection

The second important transmission route for the coronavirus is the intake of virus-containing liquid particles via the respiratory tract. Infected people expel these droplets when they breathe, speak, sing, cough or sneeze. If another person inhales these droplets, they can also become infected with the virus.

Corona infection via droplets of different sizes means that the risk of infection within a radius of one to two meters from an infected person is particularly high!

Contact and smear infection

Contact infection occurs through direct physical contact (touch) between an infected person and a healthy person, such as a hug .

In the case of a smear infection , the corona virus is transmitted through contaminated surfaces. If, for example, a person infected with corona sneezes or coughs into his hand and then attacks a door handle, he transmits the virus to the handle. If another person then grabs the handle, the viruses get onto the hand and from there, if necessary, onto the facial mucous membranes (eg of the mouth , nose) if the person concerned puts their hands there. However, such smear infections play a subordinate role in the transmission of the corona virus.

great spreader

It is now known that most infected people only infect a few or no other people, but a few infect several. People who infect a particularly large number of people are called superspreaders. You are probably highly infectious at times and have contact with many others during this time. A superspreading event is an outbreak in which many people are infected at the same time – for example at a party or event.

What is considered a critical virus contact?

The length of time someone was exposed to virus-containing particles can also affect the risk of infection with Sars-CoV-2. Since the new, more contagious virus variants have now largely established themselves, 10 minutes are now considered a critical limit in many situations.

Anyone who has had close contact with an infected person must immediately go into domestic isolation for a total of 14 days, calculated from the last risk encounter. Close contact is:

  • Anyone who has been less than 1.5 meters away from an infected person for more than ten minutes.
  • Anyone who has been in a room with a possibly higher virus aerosol load for more than ten minutes – eg at work, at a party or during sports.
  • Anyone who has had a face-to-face conversation at a distance of less than 1.5 meters with an infected person without both wearing protective masks – regardless of the length of the contact.
  • Domestic contacts of the infected person.
  • People who come into direct contact with the secretions of an infected person, eg through kissing, coughing and sneezing, mouth-to-mouth resuscitation or via vomit.

While the larger virus-containing droplets from the air we breathe quickly sink to the ground, the fine aerosols can also float in the air for a long time and disperse in closed rooms. A longer stay in a small and poorly or not at all ventilated room can therefore increase the probability of transmission of the corona virus through aerosols.

However, if an infected person coughs or sneezes directly on a person, this can already be enough for an infection. Whether or how severely someone falls ill after contact also depends on how much virus they have inhaled.

Infection even without symptoms

The insidious thing about an infection with Sars-CoV-2 viruses is that infected people can already be contagious before the first signs of illness appear. A large part of the infections probably occurs one to two days before the onset of the first symptoms. The risk of infection is greatest around the time the symptoms begin. In milder cases, it steadily decreases over the next 10 days. In severe cases and in individual cases, infection periods of up to 20 days have been observed.

There is therefore also a risk of infection in asymptomatic infected people – ie people who have been infected with Sars-Cov-2 but do not develop any symptoms. You can still pass the virus on to other people.

What does the reproduction number mean?

The number of reproductions (R) is considered an important mark for assessing the further course of the infection wave with Sars-CoV-2. It indicates how many other people are infected on average by a single infected person. For example, if the reproduction number is 0.8, 100 infected people infected 80 others. That is why politics and science are striving for an infection rate of as far below 1 as possible – then the number of infected people decreases overall.

Among other things, politicians rely on the number of reproductions when they relax measures for public life such as distance regulations or the obligation to wear masks – or tighten them again.

Corona virus: course of infection

The course of the disease in Covid-19 patients is very different. They range from completely symptom-free courses to severe pneumonia, lung failure and/or sepsis and embolism and death. Basically, the course of Covid-19 can be divided into different phases:

Stage 1: Contagion

Sars-CoV-2 viruses enter the body through the mucous membranes of the nose, mouth or eyes or are inhaled deep into the lungs. Their goal is to infect body cells. Because unlike bacteria , viruses need the replication apparatus of the cells in order to multiply. Initially, this virus multiplication mostly happens in the throat . This is why Sars-CoV-2 is so contagious – light viruses are transported from the throat to the outside by coughing, sneezing, speaking or singing.

Even before the corona viruses can penetrate body cells, they encounter the non-specific immune system – the first bulwark of the immune system against pathogens. The non-specific immune defense includes certain immune cells. They recognize that the viruses are foreign structures and fight them.

Within a few days, the body then builds up a specific defense that is specially tailored to the corona virus. These include so-called antibodies. They dock onto the pathogens and thus prevent them from penetrating body cells. They also call scavenger cells onto the scene, which “devour” the virus.

Phase 2: First signs of illness

Despite these protective measures, a certain proportion of those infected become more or less seriously ill with Covid-19. The first symptoms appear on average of five to six days after infection (= incubation period). The incubation period for the coronavirus can be as little as one day or as long as 14 days.

In the fight against the virus, the body regulates its temperature upwards, among other things – this creates an unfavorable climate for the virus. In addition, inflammatory cells migrate in large numbers to the affected body regions in order to render the virus harmless. They also destroy affected body cells.

These defensive measures are reflected in typical Covid 19 symptoms such as fever, dry cough and runny nose.

Phase 3: Worrying of symptoms

In about 80 percent of patients, the disease takes a mild or mild course. However, these patients can also feel very ill and sometimes need weeks to recover.

If the virus is not stopped, it will spread even further into the deep airways. Pneumonia can develop an average of two to seven days after the first symptoms appear.

In about 14 percent of all those affected, the lung infection is difficult: they develop severe pneumonia, with the oxygen content in the blood dropping – this causes, among other things, shortness of breath.

About five percent of patients develop an acute life-threatening course of Covid-19.

Shortness of breath warning sign!

Shortness of breath is a serious warning sign that a severe course is beginning. For example, choppy speech due to shortness of breath (staccato speech) is typical.

Even if the shortness of breath doesn’t feel threatening, you should take it very seriously and have it checked out by a doctor as soon as possible. Their condition can deteriorate rapidly as the inflammatory processes progress.

Silent lack of oxygen

In some patients with Covid-19, however, doctors also observe an unusual phenomenon: they suffer from severe oxygen deficiency without feeling it. Even life-threatening values ​​do not cause them shortness of breath. Medical professionals refer to this condition as “silent hypoxemia.”

Statistically, patients who are severely affected by Covid-19 have to go to the hospital four to eight days after the first symptoms appear.

course of pneumonia

In the case of pneumonia, fluid accumulates in the lungs, which also has poorer blood circulation. Hardly any oxygen is absorbed in the affected areas of the lungs. The patient finds it increasingly difficult to breathe.

He gets oxygen through a mask. If that is not enough, he has to be artificially ventilated in the intensive care unit – either non-invasively using a ventilation mask/hood or invasively using a ventilation tube (intubation).

More organ damage

In addition to the lungs, the virus can infect other organs – those whose cells, like those in the lungs, are equipped with receptors that the virus can use to penetrate. This applies in particular to the liver, kidneys , small intestine , testicles and heart.

Heart problems in Covid-19

Anyone with a weak heart is particularly affected by the lack of oxygen caused by pneumonia. In order to fight the consequences of infection and disease, the heart has to beat faster. Pre-damaged hearts then quickly reach the limits of their capacity.

The damage to the heart caused by the disease can also be dangerous for patients without previous illnesses. The main complications of Covid-19 in the heart include cardiac insufficiency, cardiac arrhythmia and pump failure of the heart muscle (cardiogenic shock ).

Phase 4: Life-threatening course

Around six percent of Covid 19 patients become so ill that their lives are in danger. In the case of acute and severe lung failure, there is a risk of death by suffocation. Then breathing must be mechanically assisted. The patient is then usually artificially ventilated. Non-invasive ventilation using a mask is often not sufficient. Doctors intubate the patient, which means they insert a breathing tube into the airways. To do this, they sedate the person concerned. That means they put him in an artificial coma with anesthetics.

If this artificial ventilation does not help enough, the person concerned receives what is known as extracorporeal membrane oxygenation (ECMO). The blood is enriched with oxygen outside the body and then fed back into the bloodstream. But even this does not always prevent the death of the patient.

Impending organ failure

In the case of life-threatening corona courses, the organs can finally fail completely. The reason may be insufficient breathing, which can no longer be compensated. But it is also life-threatening if the immune system reacts to the coronavirus infection with a massive counter-reaction, which can itself damage various organs.

A so-called cytokine storm develops: the immune system releases excessive amounts of messenger substances that intensify inflammatory reactions. These processes can massively affect the body and be fatal.

With such violent courses of Covid-19, the patients feel very bad, are confused and are afraid of death. Sometimes they can hardly speak and are very sleepy. You breathe fast and heavily, your blood pressure drops, your heart races. Doctors speak of a (septic or sepsis-like) shock event , which in some cases ends in death.


A Sars-CoV-2 infection also increases the blood’s tendency to clot. As a result, thrombosis develops, which can migrate to the lungs or brain or clog the fine arteries of the kidneys.


More severe courses also occur in patients who catch another infection in addition to the Covid 19 disease. Bacteria or fungi usually cause additional complications (co-infections and superinfections).

What is the death rate?

Infection with the novel coronavirus can be fatal. Researchers cannot say for sure how many people who suffer from Covid-19 die. They assume that too many cases of illness are not even known – ie Covid-19 is not always diagnosed (eg due to only mild symptoms). The sometimes very high mortality rates in various countries are due to the fact that only serious cases of illness are included in the statistics.

The differences in the Covid-19 death rate of different regions and countries are also related to different possibilities and capacities of medical care for the seriously ill. The proportion of risk patients who are ill also plays a role: for example, where more old people live and become ill, the death rate is higher.

How often an infection ends fatally can be specified with the so-called case fatality rate (CFR). This is done by dividing the number of reported deaths by the number of reported cases of confirmed coronavirus infection in a population. Accordingly, the case-deceased proportion for Europe is an estimated 10.5 percent. In Germany it is (as of September 2020) 4 percent.

However, this method is imprecise. Because it only describes the number of deaths as a proportion of the detected infections. Since the number of unreported infections is probably significantly higher, it is not (yet) possible to make a reliable statement on the death rate from Covid-19. However, experts estimate it to be around 1 percent for Germany.

However, this could change, since this value depends significantly on the virus variant circulating at the time.

Stage 5: Recovery

Patients with mild courses of Covid 19 disease usually recover within two weeks. Patients with severe symptoms need around three to seven weeks before they have largely recovered.

Consequences and complications of Covid-19

Several properties of the virus can favor severe courses.

Sars-CoV-2 affects many organs

In order to get into the body, Sars-CoV-2 uses certain receptors (docking points on the cell surface) – those for the enzyme ACE2. This is involved in blood pressure regulation, among other things.

In addition to the lungs, other organs are also equipped with ACE2 receptors and can therefore be affected by Sars-CoV-2. For example, these receptors are found on the surface of heart, blood vessel, kidney and intestinal cells.

Increased blood clotting

In the case of an infection with Sars-CoV-2, the tendency for blood to clot increases significantly. As a result, blood clots/thrombi often form, which can block vessels ( thrombosis or embolism ). This damages the organs. The function of the lungs and kidneys in particular can be impaired by such blood clots. In addition, the increased tendency to blood clots increases the risk of heart attack and stroke .

In many deceased corona patients who were examined after their death, the pathologists found thrombosis (vascular blockages caused by blood clots that had formed locally) in the legs, but also pulmonary embolisms – ie lung vessels blocked by blood clots, with the clots elsewhere ( eg in the deep leg veins) and then migrated to the lungs.

In order to prevent the formation of blood clots (with subsequent thrombosis or embolism), Covid-19 patients are given anticoagulants in many cases.

Possible reasons for the increased tendency to clot are:

  • The virus directly damages blood vessels , increasing the likelihood of thrombi.
  • The body’s massive inflammatory response to infection can disrupt blood clotting .
  • The lack of oxygen that occurs as a result of the lung attack promotes thrombosis.

Complications in the lungs

The lungs are the organ most commonly severely affected by Covid-19. The air sacs (alveoli) in which gas exchange takes place are particularly affected – more precisely the cells of the endothelium of the air sacs – a thin cell layer lining the alveoli. They perish with Covid-19.

Added to this is the inflammatory reaction of the immune system, which acts against the virus and breaks down the cells that have died after the infestation. Cell debris accumulates, mixed with inflammatory cells and fluid that leaks from the affected blood vessels. The mixture covers the alveoli like glue and impedes gas exchange. On X-rays, doctors then see a milky cloud that appears to be over the lungs (pulmonary infiltrate).

A special feature of Covid-19 is that many small blood clots can also block the finest capillaries in the lungs. This makes it even more difficult to absorb oxygen: the patient suffers from shortness of breath. In extreme cases, the lungs fail.

Although some Covid-19 patients have little oxygen in their blood, they still do not feel short of breath. How exactly this phenomenon, which is also called “happy hypoxia”, occurs, has not yet been finally clarified.

inflammation of the blood vessels

Covid-19 takes a severe course, especially in people with cardiovascular diseases. The blood vessels are also equipped with the ACE2 receptor and can therefore be attacked by Sars-CoV-2. They then become inflamed, which impairs their function. This can affect the whole body.

Heart damage in Covid-19

The heart often also suffers in severely ill Covid 19 patients: Among other things, Chinese researchers reported early on that one in five Covid 19 patients in the hospital already showed acute damage to the heart muscle.

It was unclear whether this was a direct result of the infection or, for example, a result of the hard work that the heart had to do due to the infection in the body. What is certain is that heart cells are also equipped with the ACE2 receptor and can therefore be infected themselves.

kidney failure

The second most commonly affected organ by Covid-19 is the kidney. In 30 to 50 percent of seriously ill patients, these important detoxification organs of the body fail, 20 to 25 percent even need dialysis (blood washing). There are many possible reasons for this:

Clots : One explanation here is the increased tendency of the blood to clot due to the coronavirus infection. Clots then often block the renal vessels. Areas of the organ that are undersupplied with blood die as a result.

Medications : Medications administered to treat pneumonia in Covid-19 also play a role. Patients are given draining drugs to eliminate excess fluid in the lungs. However, these can put a strain on the kidneys.

Damage from the virus itself : There is also evidence that the coronavirus attacks the kidneys directly. ACE2 receptors are also found on kidney cells as potential docking sites for the virus. So far, nothing can be said about the long-term consequences of such kidney damage.

Immune system overreaction : What is known as a cytokine storm, the overreaction of the immune system to infection, can also damage the kidneys.

Involvement of nerves & brain

According to current knowledge, Sars-CoV-2 infections can also affect the nervous system. Neurological complaints can be explained, for example, with the reaction of the immune system to the infection. The release of immune messengers (cytokines) causes the blood-brain barrier , which normally protects the brain from harmful substances, to become more permeable. Substances that are normally held back can then pass from the blood into the brain.

In addition, there are initial indications that the virus can cause changes in the brain. This is especially true in the case of severe disease progression. The case study of a Japanese man who was treated in hospital for epileptic seizures caused a stir. The doctors found the virus in the cerebrospinal fluid in his brain.

According to current knowledge, a coronavirus infection can cause the following neurological complications:

A characteristic and noticeable sign of Covid-19 is the sudden loss of the sense of taste and smell. It can last for weeks. It is believed that the virus can damage the olfactory nerves in the nasal mucosa. The olfactory nerve originates directly from the olfactory bulb – and is therefore part of the brain stem.

An unusual phenomenon of Covid-19 is shortness of breath without severe pneumonia. This phenomenon could be triggered by an attack on the respiratory center in the brain.

Likewise, infection with Sars-CoV-2 can cause Guillain-Barré syndrome (GBS). This is an inflammatory nerve disease that is associated with symptoms of paralysis and sensory disturbances.

Elevated liver values

According to the current state of knowledge, the liver is probably not directly attacked by Sars-CoV-2. Nevertheless, the liver values ​​​​of many seriously ill patients increase. The cause is, on the one hand, the burden on the liver caused by the medication administered. On the other hand, the extensive infection process can damage the liver.

Post Covid: consequential damage from Covid-19

Once the patient has overcome the coronavirus infection, it can take weeks and months to fully recover. Studies have shown that symptoms can still occur up to 60 days after the onset of symptoms. This phenomenon is also called “Post-Covid-19 Syndrome” or “Long Covid” . Some survivors also appear to have permanent damage. However, only a very small proportion of those infected are affected.

What long-term damage a Sars-CoV-2 infection can cause and how often this is the case has not yet been finally clarified. Initial studies suggest that one in ten patients (including those who are mildly ill) could still suffer from complications for weeks and months, and up to 80 percent of all those patients who had to be treated in hospital.

More detailed information on the symptoms, causes and prognosis of an existing post-Covid syndrome (Long Covid) can be found here .

immunity after infection

Anyone who becomes infected with Sars-CoV-2 develops specific antibodies against the virus that can make you immune. However, it is not yet possible to estimate how long this immune protection will last. In the case of mild illnesses in particular, the immune response is probably less strong.

However, that does not mean that the body is not prepared to defend itself against renewed Sars-CoV-2 pathogens. Other immune cells, so-called T-cells but also B-cells, are also crucial for the long-term immune response. Thanks to the immune memory, the body can quickly produce specific antibodies again if it encounters the new corona virus again.

You can find out more about this in the article ” Sars-CoV-2: The big question about immunity “.

Covid-19: risk factors for severe course

Severe courses of the disease from Covid-19 are observed more frequently in some groups of people. These groups are therefore considered to be coronavirus risk groups:

  • Older people : The risk of a severe course of Covid-19 increases from the age of around 50 to 60 years.
  • smoker
  • severely overweight people ( BMI >30); especially young patients and men
  • People who are underweight (BMI below 18.5)
  • Pre -existing conditions, especially those suffering from any of the following conditions:
    • Cardiovascular diseases such as coronary artery disease , high blood pressure, heart failure (weak heart)
    • chronic lung diseases such as pulmonary fibrosis, COPD
    • chronic liver disease such as cirrhosis
    • Diabetes (diabetes mellitus)
    • Cancer
    • People with a weak immune system, for example due to an immune-weakening illness or because of the regular intake of medication that suppresses the immune system (e.g. cortisone, rheumatism or cancer medication)

Although men do not fall ill more often than women, they have a more severe course. Physical condition can also influence how severe Covid-19 will be in a patient. The assessment of the personal risk for a severe course is therefore complex and is therefore carried out by the doctor.

Severe and critical courses of Covid-19 can also occur in people who do not belong to any of the risk groups mentioned above. Even younger and otherwise healthy people can become seriously ill with Covid-19 – or even die.

Blood group as a risk factor?

Several studies suggest that people with blood group A are more easily infected with Sars-CoV-2. People with blood group 0 are affected less frequently. The severity of the Covid 19 course also seems to be related to the blood group.

However, studies from the USA showed that this connection can no longer be proven if other diseases or risk factors are also considered. In addition, further research is needed to clarify how exactly the blood group can influence a coronavirus infection or Covid-19.

Covid-19 in pregnancy

Pregnant women are usually quite young. Experts assume that the vast majority of them will only develop mild to moderate symptoms if they contract Sars-CoV-2.

Slightly increased risk of severe courses

However, the risk of a severe course of Covid-19 appears to be slightly higher in pregnancy than in non-pregnant infected women of childbearing age. For example, pregnant women who are ill have to be treated in intensive care or ventilated a little more often.

This applies in particular to pregnant women who bring additional risk factors with them: a high body mass index (BMI), diabetes, advanced age or high blood pressure.

Premature births and miscarriages are rare

There is evidence that Covid-19 disease in pregnant women could slightly increase the risk of premature birth or miscarriage. In individual cases, it was also documented that the child had been infected in the womb. However, as far as is known, these children have recovered well from the infection.

Pregnant women do not have to worry too much in the event of an infection. Nevertheless, you should take special care not to get infected in the first place – also because some medications and treatment methods are associated with risks for the child.

You can read more about infection with Sars-CoV-2 during pregnancy in the article: ” Coronavirus: What pregnant women need to know now “.

You can find out what pregnant women should know before giving birth in the article “Birth in times of the corona pandemic – the most important information”.

Covid: 19 examinations and diagnosis

If you suspect that you are infected with the corona virus or have Covid-19, the first step is to call your family doctor. He will discuss with you the details of a coronavirus test and necessary investigations.


First, the doctor collects your medical history ( anamnesis ). He will ask you about your symptoms and risk factors for infection. Possible questions are for example:

  • What complaints do you have?
  • When did the first symptoms appear?
  • Have you been to a coronavirus risk area?
  • Has your sense of taste or smell changed?
  • Have the symptoms changed, possibly worsened?
  • Do you feel short of breath?

If necessary, also inform your doctor about known previous or underlying diseases (such as diabetes) as well as about medications that you are taking. Also consider whether you may have had contact with possible Covid 19 patients.

Physical examination

During the physical examination, the doctor focuses on the condition and functioning of the airway.


The doctor first examines and examines the patient’s body and skin. This gives him information about his physical condition. He may already notice pathological changes, such as cyanosis (bluish discoloration of the skin and fingernails due to lack of oxygen).


Next comes the palpation. This means palpating the patient with the hand. The doctor places his flat hand on the patient’s upper body, who says “99” several times in a voice that is as deep as possible. The doctor can feel whether there are changes in the lungs – for example fluid in the lungs.

percussion (tapping)

The doctor taps either with the fingertip or with a so-called percussion hammer on a special plate (plessimeter) or on a finger placed underneath the other hand. The knocking sound changes over a cavity or particularly dense tissue.


An important point in case of suspected Covid-19 is listening to the chest. He checks the breathing sounds with a stethoscope. If you notice a rattle, for example, this can be an indication of pneumonia.

urine test

If a patient has to be treated in hospital and is proven to be infected with Sars-CoV-2, a urine test (several times if necessary) should always be carried out. The doctor determines the content of albumin , erythrocytes and leukocytes in the urine. If these values ​​​​are elevated, this indicates an involvement of the kidneys. In addition, the risk of a severe course of the disease is often increased.

blood test

In the course of the examination of Covid-19 patients in the hospital, the doctor will take at least one blood sample. Because the blood values ​​​​can, for example, give an indication of whether the heart is being damaged by the infection.

Among other things, the following blood values ​​are determined during the examination:

  • Troponin : If the value of troponin T or troponin I is at the upper limit of the reference range, this indicates a severe course of the disease.
  • CRP (C-reactive protein): The protein is involved in inflammatory processes and is elevated in 58 percent of Covid-19 patients.
  • LDH (lactate dehydrogenase): If this enzyme occurs in the blood, it indicates cell damage in the body. In the case of an infection with Sars-CoV-2, the value is often increased.
  • AST ( aspartate aminotransferase, formerly glutamic-oxaloacetic transaminase/GOT): If this liver value is increased, the liver can be damaged.
  • Albumin: Three quarters of Covid-19 patients have low levels of albumin.
  • D-dimers : These are breakdown products of the fiber protein fibrin, which plays an important role in blood clotting. They are done to rule out thromboembolism, which is a sudden blockage of a vein or artery by a blood clot.
  • Leukocytes: In a third of patients, the number of leukocytes (white blood cells) is too low.
  • Lymphocytes : The number of this subset of white blood cells can be used as a diagnostic marker. The lymphocyte value is increased in 82 percent of Covid-19 cases.

Electrocardiography (ECG)

If the troponin level is significantly elevated, the heart is examined more closely. An electrocardiography (ECG) follows. The doctor measures the electrical activity of the heart using electrodes attached to it. The heart action is recorded in the form of curves. The doctor may use this to assess whether the heart is functioning properly or not. In this way, possible damage caused by Sars-CoV-2 can be detected at an early stage.

imaging procedures

In the case of severe Covid 19 symptoms such as shortness of breath, the patient must be examined more closely in the hospital, including with imaging methods:

Usually an X-ray examination of the chest ( X-ray thorax ) and an ultrasound examination of the lungs are ordered. Doctors can use it to detect pneumonia, for example. In case of doubt, imaging is performed using computed tomography (CT). A magnetic resonance imaging (MRI) of the lungs or the heart can also be useful.

If neurological complications are suspected, a CT or MRI is always performed.

The imaging methods mentioned are also used to monitor the course of the infection and are therefore sometimes repeated several times.

Further measures

The oxygen saturation in the blood can be determined using an external sensor (eg a finger clip) or by blood gas analysis. The latter also shows, for example, how much carbon dioxide is in the blood.

Other important metrics are:

  • body temperature
  • blood pressure
  • respiratory rate
  • heart rate

Corona virus test

Whether someone actually has an infection with the corona virus can only be clearly clarified with a special corona test.

A distinction is made between the following procedures:

  • PCR test – to detect viral genetic material
  • Antigen test – to detect specific proteins of the virus
  • Antibody test – to detect specific antibodies to the virus

PCR test

A PCR test can reliably detect even the smallest amounts of genetic material. The test is therefore considered the “gold standard” for detecting a Sars-CoV-2 infection.

As a rule, the corona PCR test can detect an infection two to three days before and up to 20 days after the onset of symptoms. In individual cases, proof is even possible 60 days after the onset of the symptoms of the disease.

So at the very beginning, this coronavirus test can be negative, even though an infection is present. If there is still a suspicion of Covid-19, doctors then usually carry out another Covid-19 test after two to three days.

Further information on the detection of coronavirus using the PCR method can be found here .

antigen testing

Unlike the PCR test, antigen tests do not detect the Sars-CoV-2 genome, but certain proteins that are specific to the virus. They provide a result within 15 minutes.

Therefore, antigen tests are suitable for testing new arrivals in hospitals or nursing homes and thus quickly separating infected people from the rest. Since they are also comparatively cheap, they can also be used routinely to test people who are at risk. However, antigen tests are less reliable compared to PCR tests.

See our Rapid Antigen Tests article for more information.

Corona self test

A corona self-test is an antigen test that you can carry out yourself and that works in a similar way to a pregnancy test . So you can use it at home. The tests are now available in pharmacies, drug stores and even discounters.

Self-tests are useful in situations where a quick result is important. This can be in the run up to a meeting with family or friends. With a corona self-test, you can reduce the risk of “silent transmissions”, especially in the case of courses with few symptoms.

You can find detailed information on the subject of coronavirus tests for self-testing in our special topic .

antibody test

In addition to the PCR and antigen tests, which are intended to detect an acute infection, there are corona antibody tests. With them, a blood sample can be used to determine whether a person was previously infected with Sars-CoV-2.

The test reacts to special defense proteins (immunoglobulins) that circulate in the blood. The immune system forms them during the course of the disease in order to take targeted action against Sars-CoV-2.

Detailed information on the subject of antibody tests can be found here .

Coronavirus: Vaccination

So far, five vaccines against the coronavirus have been provisionally approved in the EU. Studies confirm that all available vaccines are highly effective. However, it is still unclear how long the immune protection lasts. According to the World Health Organization, more than 200 other vaccine candidates are still in development. It is still unclear which of these candidates will ultimately be admitted.

Further information on the effectiveness, the side effects and the principle of action of all coronavirus vaccines currently available in Germany can be found here .

Corona vaccinations: side effects

Like all medicines, the corona vaccines also have side effects. Typical vaccination reactions subside after hours to a few days. This includes:

  • headache
  • Pain and swelling at the injection site
  • fatigue
  • fever and chills
  • Muscle aches

Allergic symptoms can also occur, although severe anaphylactic reactions are very rare.
You can read more information about possible side effects and the question of rare and long-term consequences in the article: Covid-19 vaccinations: side effects .


Until vaccination gives large parts of the population immunity to the virus, other preventive measures are particularly important.

Influenza and pneumococcal vaccination

One of the preventive measures against Covid-19 is to look at the yellow vaccination card. Influenza and pneumococcal vaccinations cannot prevent coronavirus infection. However, pneumococcal disease or influenza can make the course of Covid-19 significantly more difficult. Because then the body has to fight two infections at the same time.

The Standing Vaccination Committee (STIKO) of the Robert Koch Institute generally recommends that people with certain previous illnesses and older people be vaccinated against influenza and pneumococci.

You can find out when the STIKO recommends which vaccination in our topic special ” Vaccinations “.

prevent infection

The so-called AHA rules help to prevent infection with Sars-CoV-2. AHA stands for:

  • keep your distance
  • Observe hygiene measures
  • wear everyday masks

Further measures consist of regular, extensive ventilation and the use of the Corona-Warn-App .

keep distance

A crucial measure to avoid infection with the coronavirus is to keep a sufficient distance from (potentially) infected people. The rule does not only apply to people who have been proven to be infected: In order to protect against infection, make sure you keep a sufficient distance from other people in everyday life. In this way, you can reduce the risk of asymptomatic infected people transmitting the virus to you unnoticed.

hygiene measures

Thorough hygiene is also important in the fight against the Covid 19 pathogen. Above all, wash your hands regularly and thoroughly – for at least 20 seconds, with warm water and soap. Hand disinfectants from the “limited virucidal” level are also suitable for ridding hands of viruses.

everyday masks

The so-called everyday masks are simple mouth and nose covers made of fabric. They can intercept some of the respiratory droplets and thus – in the event of an infection – protect other people from their own virus-containing droplets. Everyday masks protect the wearer less well. But especially if they are worn across the board by the population, they can significantly curb the transmission and spread of Sars-CoV-2.

There are basically different types of mouth and nose covers that can serve as a barrier in front of the airways:

  • disposable masks
  • self-sewn reusable masks (everyday masks)
  • medical masks
  • Scarves, shawls or other items of clothing

In the course of the 2020 coronavirus pandemic, the German government introduced a mask requirement. Wearing a mouth and nose cover is mandatory in public transport and shops. You can find out more about this in the article ” Mask requirement: The most important information “.

Corona warning app

The federal government’s Corona warning app has been available since mid-June 2020. It should help to quickly trace chains of infection. The Corona-Warn-App works via Bluetooth. In this way, the mobile phone determines how close a person is to another person who also has the app installed. The duration of the encounter is also recorded. Anyone who has had contact with a person who has been proven to be infected will then receive a warning.

You can find out exactly how the app works in the article ” Corona Tracing App: The most important facts “.

break the chain of infection

If you want to break the chain of infection, infected people must be identified quickly (using a test) and isolated. It is just as crucial that contact persons of people affected by Corona from the professional and private environment are quickly found and also tested. Those affected must go into quarantine at home for 14 days.

The aim of the measures is above all to avoid a rapidly increasing number of infections and thus a wave of Covid 19 diseases. This is intended to protect the supply structures (e.g. rescue services, hospitals) from being overloaded.

Be careful when travelling

Since the corona virus has spread worldwide, it is important to ensure that all safety precautions and hygiene measures are observed when travelling.

The Federal Foreign Office has issued travel warnings for different countries due to Sars-CoV-2. These are countries with high infection rates.

You can find out which countries these are in the article ” Coronavirus: These are the risk areas “.

If you are planning a holiday or another trip, then find out in advance about the applicable regulations in the holiday country and about the possible consequences on the return journey. When returning to Germany from abroad, a corona test or a precautionary quarantine at home may be required. This should prevent the number of infections nationwide from flaring up again.

Covid-19 in children

Children may contract the corona virus less often than adults – they make up fewer people who have tested positive. However, the number of unreported cases could be particularly high for them, since they develop no symptoms more often than adults. If they fall ill, the course of the disease is also significantly milder, and severe courses are rare. So far, only isolated deaths in children in connection with Covid-19 are known. The reason for this is so far unclear.

How contagious are children with Covid-19?

It is also not possible to conclusively assess how contagious infected children are. Previous investigations have yielded different results. However, experts are currently assuming that there is no significant difference between children and adults in terms of contagiousness (infectivity). However, young children tend to be less contagious than older children, adolescents and adults.

The role schools play in the spread of the pandemic has also not yet been fully clarified. You can find out the state of knowledge on this topic in the article Corona spread: What role do schools play? .

Covid-19 symptoms in children

When children contract Sars-CoV-2, the infection is usually mild in most cases. This means that most children show no or hardly any symptoms. Scientists also use this to explain the comparatively low number of cases: Since children develop symptoms less often, they are also tested less frequently.

Various corona symptoms can also occur in children. This includes:

Gastrointestinal complaints (such as diarrhea) with Covid-19 are more common in children than in adults. However, some children do not develop any typical symptoms at all, such as coughing, shortness of breath or pneumonia.

Infected but apparently healthy children – like adults – can spread the virus!

Risk factors and complications in children

Even in infants and small children, Covid-19 can sometimes be difficult – but less often than in adults.

Pre-existing conditions play an important role in the course of the coronavirus infection in children, in particular:

  • Lung diseases such as asthma
  • Heart disease, such as a congenital heart defect

Hyperinflammation Syndrome in Covid-19

Pediatricians are increasingly reporting on inflammatory reactions that can occur throughout the body of corona-infected children. The European disease agency ECDC calls the clinical picture “pediatric inflammatory multisystem syndrome (PIMS)” in combination with a “toxic shock syndrome (TSS). This PIMS-TSS is similar to Kawasaki syndrome , severe vascular inflammation ( vasculitis ) in childhood.

This severe inflammation can also occur with other infectious diseases. Overall, however, these are a rare complication. The German Society for Pediatric Infectious Diseases (DGPI) emphasizes that this accumulation of hyperinflammatory syndrome in connection with Covid-19 must be monitored further. There is a separate register for this.

So far, there is no direct evidence that the infection with Sars-CoV-2 is the cause of the hyperinflammatory syndrome.

Symptoms of hyperinflammatory syndrome

The following symptoms occur during the course of hyperinflammation:

  • fever
  • skin rash (exanthema)
  • conjunctivitis
  • Polyserositis (inflammation of the body cavities)
  • Gastrointestinal complaints
  • edema
  • shock


In most cases, antibiotic therapy is initiated. In addition, doctors administer anti-inflammatory steroids (such as dexamethasone, high-dose immunoglobulins and sometimes also acetylsalicylic acid ) in the case of hyperinflammation. If the treatment does not work, the use of interleukins can be discussed.

In most cases, these hyperinflammatory syndromes were under control within a few days. Only in isolated cases did the children have to be treated with extracorporeal membrane oxygenation (ECMO) for acute lung failure.

The psychological consequences for children and young people

Everyday life under pandemic conditions has changed the everyday life of children and young people significantly. Limited contact options in daycare, school or sports club. These restrictions, some of which are considerable, mean great mental stress. As a result, mental health problems have increased significantly during the pandemic. As a result, some of the children developed behavioral problems or even mental disorders.

You can find more information about the psychological consequences in children and young people, the symptoms and tips for coping with these stressful circumstances here .

Frequently asked questions about Sars-CoV-2

Do you have questions about the corona virus? On the ” Coronavirus infection ” topic page you will find answers to the most frequently asked questions about the coronavirus in an FAQ.

You may also like

Leave a Comment