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Zika Virus Infection: Risks, Contagion

by Josephine Andrews
Published: Last Updated on 160 views

Zika virus infection is primarily transmitted to humans by mosquitoes. Fever, joint pain and conjunctivitis are typical symptoms. Zika virus infection in pregnant women can be passed on to the child and cause serious harm. Serious complications can also occur in adult infected people. Read here when you are at risk of contracting Zika, how the disease progresses and how you can protect yourself.

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.

G61 A92 Q02

Zika virus infection: description

Zika virus infection triggers a febrile infectious disease (Zika fever). The pathogen, the Zika virus, is mainly transmitted by mosquitoes of the Aedes genus genus .

According to the Federal Ministry of Health, only about a quarter of those infected develop the typical Zika virus symptoms. The course of the disease is usually mild. However, infected pregnant women can transmit the pathogen to their unborn child.

In 2015, more cases were reported, especially from Brazil, in which newborns of infected mothers had a head that was too small (microcephalus). This misdevelopment is usually accompanied by brain damage and severe intellectual disability.

A Zika infection could also increase the risk of the otherwise very rare Guillain-Barré syndrome in adults – a disease of the nerve tracts that can cause severe paralysis.

Zika virus infections have been notifiable in Germany since 2016.

The Zika virus

The Zika virus belongs to the Flaviviridae family and the Flavivirus genus. This group also includes, for example, the virus of tick-borne encephalitis (TBE), a dangerous meningitis or encephalitis. Other known flaviviruses are dengue, West Nile and yellow fever virus.

Spread of Zika virus infection

Zika viruses are found in all tropical and subtropical regions, especially in Africa, Southeast Asia and the Pacific Islands. Between 2015 and 2017 there were also major outbreaks in Central and South America. In autumn 2019, isolated Zika virus infections even occurred in southern France.

Researchers first discovered the Zika virus in a rhesus monkey in Uganda’s Zika forest in 1947. The first Zika virus infections in humans were detected in 1952 in Uganda and Tanzania. In 2007 there was a first major outbreak on the western Pacific Yap Islands (part of Micronesia). 75 percent of the local population fell ill with a Zika virus infection. A wave of infections followed in French Polynesia in 2013. At that time, about ten percent of the population fell ill.

In the meantime, the virus has continued to spread. However, it was only the major Zika outbreak in Brazil in 2015 that attracted international attention, particularly because it was here that scientists were able to establish a link to microcephaly in children infected in the womb for the first time.

From then on, the virus spread rapidly across the South American continent and also reached Florida in the US. However, according to the CDC, there are currently no local transmissions in the United States.

Travel warning for regions with Zika virus infection

Due to its spread, Zika virus infection is now considered a travel sickness. Travelers become infected in the affected countries and bring the virus home with them, where they can infect others, for example during sex. If the mosquito species that transmit the virus are missing in the home countries, larger outbreaks are impossible. This is the case in Germany, for example.

Travel warnings for pregnant women apply to risk regions. In addition, holidaymakers should protect themselves there more against mosquito bites in order to prevent a Zika virus infection.

Zika virus infection: symptoms

Zika virus infection is often asymptomatic, i.e. without symptoms.

If symptoms do occur, the disease usually takes a mild course. The first Zika virus symptoms appear about two to seven, sometimes twelve days after infection ( incubation period ). The signs are similar to those of other mosquito-borne viral diseases, particularly dengue or chikungunya fever. Those affected usually suffer from the following symptoms:

  • Slight fever (“subfebrile” temperatures around 38 degrees Celsius)
  • nodular-patchy skin rash (maculopapular exanthema)
  • Joint pain (arthralgia)
  • red eyes caused by conjunctivitis

Some patients feel very ill and exhausted and also complain of headaches and muscle pain. In rare cases, sufferers also report dizziness and stomach pains , nausea with vomiting and diarrhea.

Serious disease progressions, such as those that can occur with dengue (bleeding due to a massive drop in blood platelets) or chikungunya (month-long joint pain, bleeding), are very rare with a Zika virus infection. However, it can be dangerous for pregnant women and their unborn children. There is also a possible connection with Guillain-Barré syndrome.

Zika virus infection in pregnant women

A Zika virus infection usually heals after a few days without any consequences. Only the rash lasts about a week. However, it can become dangerous if pregnant women become infected with the Zika virus. The pathogen can then pass to the child via the blood – even if the pregnant woman does not feel any symptoms herself.

The Zika virus can massively disrupt the development of the unborn child and cause microcephaly, for example. The children are born with a (micro) head (-cephalus) that is too small. The brain is often damaged and the child affected is mentally handicapped.

The virus can stay in the body for weeks to months. After that, there is probably lifelong immunity. If a woman becomes pregnant weeks after the Zika virus infection has healed, there is probably no longer any risk for the child.

Guillain-Barré syndrome after Zika virus infection

A Zika virus infection can also have dangerous consequences for infected adults. In some cases, it causes Guillain-Barré syndrome. This is a rare neurological disease that manifests itself in paralysis, which in the worst case can also affect the respiratory muscles. About 20 percent of the patients remain physically disabled, about five percent die.

Zika Virus Infection: Causes and Risk Factors

Transmission of the Zika virus

According to current knowledge, the Zika virus is only transmitted to humans by mosquitoes of the Aedes genus. Well-known representatives are Aedes albopictus ( Asiatic tiger mosquito ) and Aedes aegypti ( Egyptian tiger mosquito). ), which can also transmit yellow fever, chikungunya and dengue viruses, among other things.

After transmission, the single-stranded RNA virus enters human cells. Exactly how this works and what then happens in detail is still the subject of investigations. As a rule, invading viruses use use human cell components to multiply.

The viruses circulate in the blood. So, if an infected person becomes infected again from Aedes mosquitoes, they absorb the pathogens with the blood and can transmit them to other people during the next blood meal. This is how a Zika virus infection can spread in the population.

Incidentally, in addition to humans, primates are also considered to be the main carriers of the Zika virus.

Among the dangerous mosquitoes, the Asian tiger mosquito (Aedes albopictus) is particularly noteworthy. It is about five millimeters small, black and silver-white striped and widespread. According to the Federal Environment Agency, the Asian tiger mosquito has been detected in 26 countries and is considered established in 19. In the meantime, she also performs regularly in Germany.

Zika virus infection during sex

An infected person can transmit the Zika virus to another person through sexual contact – even if the infected person no longer feels any symptoms. Men in particular are carriers, presumably because the virus manages to hide from the immune cells in the shielded area of ​​the testicles for longer.

Male travelers from Zika regions should therefore use condoms during sex for around three months after their return home , as they could excrete viruses via semen for that long. Women, on the other hand, probably only transmit the virus during sex in the acute stage of the disease.

Zika virus infection via blood products

Theoretically, the Zika virus can also be found in blood transfusions. However, transmission in this way is considered extremely unlikely and has so far only been proven in a few cases. Nevertheless, travelers returning from affected regions are not allowed to donate blood for a few weeks.

risk groups

As for other infectious diseases, the same applies to the Zika virus infection: people with previous illnesses (such as high blood pressure, diabetes, heart failure), a weakened immune system (e.g. due to an HIV infection) and the elderly are particularly at risk.

In view of the increased number of newborns with small heads (especially in Brazil), pregnant women form a special risk group. However, research is still needed to determine exactly how Zika virus infection affects unborn babies. After birth , Zika virus infection is relatively harmless in both children and adults.

Zika Virus Infection: Investigations and Diagnosis

If a Zika virus infection is suspected, there is initially no reason for particular concern. The disease is usually mild and subsides after a few days without consequences. However, if you have returned from a holiday trip or have otherwise had contact with people who may have been infected, you should always consult your family doctor or a specialist in tropical medicine.

Zika virus symptoms such as fever, joint pain and rash also occur with other travel diseases that can take a much more severe course (e.g. dengue fever). A doctor’s visit is also advisable for pregnant women, since a Zika virus infection can cause harm to the unborn child – especially at the beginning of pregnancy.


The doctor will first take your medical history (anamnesis). He will ask you about your symptoms and recent trips. Possible questions are for example:

  • How long have you had your complaints?
  • When was the last time you were abroad?
  • Where did you go and how long did you stay there?
  • Have you been bitten by mosquitoes?
  • Have you recently measured an elevated body temperature?
  • Have your symptoms subsided in the meantime and are they increasing again?
  • Do you have joint pain, red eyes or skin rashes?

Physical examination

After the detailed questioning, your doctor will examine you physically. Among other things, he will take your body temperature, feel the lymph nodes and examine the skin for possible rashes. He will also pay attention to your joints and rule out other possible causes of joint pain. Red eyes provide the doctor with a decisive indication of conjunctivitis.

laboratory tests

In order to be able to diagnose Zika virus infection, the doctor must draw blood from you. Some blood values ​​can deviate from the normal value. For example, the levels of white blood cells ( leukocytes ) and blood platelets (thrombocytes) are reduced in Zika virus infection. On the other hand, other values ​​such as the C-reactive protein (CRP) are increased.

Such changes are also found in many other diseases, so they are not evidence of a Zika virus infection. The diagnosis can only be made with certainty if there is evidence of a pathogen can be detected – more precisely: if the Zika virus genome can be detected in the blood and/or urine. This detection is carried out using a special laboratory method, the “reverse transcriptase polymerase chain reaction” (RT-PCR). This allows even small traces of Zika virus RNA to be duplicated and determined.

Direct detection of the pathogen via the virus genome is only possible in the acute stage of the infection:

  • Up to the 7th day after the onset of symptoms, it makes sense to test the patient’s blood and urine samples for Zika virus RNA.
  • From the 8th to the 27th day after the onset of symptoms, a blood sample is examined for viral RNA. In addition, one checks whether specific antibodies against the pathogen can be found in the blood (serology).
  • If the onset of symptoms is more than 28 days ago, an infection can only be detected via specific antibodies in the blood.

These laboratory methods sometimes give false results because the substances used also react with other flaviviruses (cross-reactivity). In the so-called neutralization test, on the other hand, reliable detection of the Zika virus infection is possible. However, this method takes several days and is very complex. Therefore, the faster and cheaper RT-PCR is the standard procedure.

exclusion of other diseases

When examining for a possible Zika virus infection, the doctor must rule out other diseases with similar symptoms (especially other tropical/travel diseases) (differential diagnosis). This is very important because, while Zika virus infection is usually harmless, other diseases can have serious complications that start with similar symptoms.

The focus is on dengue and chikungunya. However, leptospirosis, malaria, diseases caused by rickettsia or alpha viruses (e.g. O’nyong-nyong, Ross river), rubella and enterovirus or parvovirus infections can also trigger symptoms similar to those of the Zika virus. The following table compares Zika virus infection with chikungunya and dengue fever:

symptom chikungunya dengue Zika virus infection
Fever suddenly, up to 40 degrees Celsius gradually increasing if at all, then usually only a slight fever, rarely above 38.5 degrees Celsius
fever duration usually only a few days, two peaks with a fever break in between one week only a few days
patchy lumpy rash often Rare frequent, lasting about six days
bleeding (hemorrhagic fever) Rare almost always not known
joint pain almost always and long-lasting (partly months) rarely and if so, of significantly shorter duration Yes, but also only a few days
conjunctivitis Rare Rare often

In addition, white blood cell counts are usually more significantly reduced in chikungunya than in Zika virus infection or dengue. The blood platelets, on the other hand, fall into a critical range, especially in dengue fever.

The following always applies: If you have possible Zika virus symptoms or other signs of illness during or after a trip, especially to risk areas, you should consult a doctor immediately.

Zika virus: treatment

There is no therapy that works directly against the Zika virus. Only symptomatic Zika virus treatment is possible, i.e. treatment of the symptoms:

Bed rest and adequate fluid intake are recommended , as the body can lose a lot of water during the illness phase. Medications to relieve pain and reduce fever may also be useful. Both effects can be achieved with paracetamol , for example , which is often recommended for this purpose in the case of a Zika virus infection. In contrast to other antipyretic painkillers such as acetylsalicylic acid (ASA), ibuprofen or other so-called NSAIDs (non-steroidal anti-inflammatory drugs), paracetamol does not increase the risk of bleeding.

NSAIDs should never be taken, especially in unclear cases! This could be dangerous if it is not a Zika virus infection but dengue fever. This condition can cause internal bleeding, which would be made worse by NSAIDs.

If there are other symptoms of a Zika virus infection such as conjunctivitis, the doctor will expand the treatment accordingly.

Zika virus infection: disease course and prognosis

Zika virus infection often goes without signs of illness. Many infected people do not even notice that they are carrying the virus. If symptoms occur, the symptoms usually only last a few days to a week. The rash usually lasts the longest. Hospital treatment is only necessary in exceptional cases.

As mentioned above, possible complications of a Zika virus infection are malformations in unborn children and Guillain-Barré syndrome in adult patients.

Prevent Zika virus infection

In risk areas, it is very important to protect yourself from risky mosquito bites. Even those who are already infected should definitely avoid further mosquito bites in the first week, so that the infected animal does not infect other people.

The following measures will protect you from bites:

Use insect repellent

So-called repellents with the active ingredients DEET, Icaridin or IR3535 are effective. For herbal remedies, experts recommend those based on lemon eucalyptus oil (PMD/Citriodiol).

However, health authorities do not recommend using repellents on babies younger than two months. To also protect newborns from Zika virus infection, you should cover their body completely with clothing and equip strollers and seats with mosquito nets.

Wear long pants and long-sleeved clothing.

The less bare skin you show, the less surface you offer the bloodsuckers. For extra protection against mosquito bites and thus against Zika virus infection, you can spray your clothing with the insecticide permethrin.

Use mosquito nets.

Put mosquito nets especially over your sleeping place and on the windows. For extra protection, you can spray the mosquito net with permethrin. Please note that high exposure to the sun eliminates the permethrin protection.

Avoid and eliminate water points.

Mosquitoes, which can transmit Zika virus infection, multiply at water points. Therefore, empty water and rubbish bins regularly or cover places where moisture can give rise to new mosquitoes (plant pots). If possible, do not move into your holiday accommodation in the immediate vicinity of ponds or similar water points. Insecticides may need to be used.

Do not travel to risk areas if you have health problems or are pregnant!

Follow the current recommendations of the health authorities. Further information on the current situation regarding Zika virus infections can be found, for example, on the websites of the World Health Organization, the Federal Foreign Office and the European or American health authorities (ECDC, CDC).

Tell your doctor about previous trips!

This is especially true for pregnant women returning from a risk area. Tell your gynecologist about your trip at the latest at the next check-up. If you become ill, you will be tested for Zika virus infection and further investigations will be initiated if necessary. If you feel healthy, your doctor uses the information to pay particular attention to early signs of defective brain and skull development in the child in the ultrasound .

Not only with a Zika virus infection, but in general:

Consult a doctor immediately if you suffer from symptoms of illness such as fever, red eyes, skin rash, nausea, headache and body aches – especially on or after traveling to risk areas! Don’t be afraid to visit clinics in your travel country if necessary. In this way, other, more severe diseases can also be detected and treated at an early stage.

Zika virus: vaccination?

A medicinal precaution against a Zika virus infection in the sense of a vaccination is not yet possible. However, studies are ongoing.

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