Zika virus infection

Zika virus infection: description

A Zika virus infection triggers a feverish infectious disease (Zika fever). The pathogen, the Zika virus, is transmitted to humans by mosquitoes of the Aedes genus.

On average, about every fourth to fifth develops typical Zika virus symptoms. The course is usually mild. However, infected pregnant women can transmit the pathogen to their unborn child. More cases have been reported, especially from Brazil, where neonates of infected mothers had too small a head (microcephalus). This maldevelopment is usually associated with brain damage and severe mental retardation. In addition, the suspicion that a Zika infection could cause the otherwise very rare Guillain-Barré syndrome – a disorder of the nerve tracts, which can be associated with severe paralysis.

Spread of Zika virus infection

The Zika virus was discovered in 1947 by a rhesus monkey in Uganda’s Zika forest and named after it. The first Zika virus infections in humans were described in 1952 in Uganda and Tanzania. In 2007, there was a first major eruption on the western Pacific Yap Islands (Micronesian state). 75 percent of the population there fell ill with a Zika virus infection. In 2013, a major outbreak followed in French Polynesia. Here, about ten percent of the population fell ill.

Meanwhile, the virus has spread further and further. However, international attention was given to the big Zika outbreak in Brazil in 2015, especially since this was the first time that the connection to microcephaly in infants infected in the womb had been established.

Since then, the virus has spread rapidly across the South American continent and has reached Florida in the US.

Travel warning for regions with Zika virus infection

Due to its spread, a Zika virus infection is now one of the travel diseases. Travelers are infected in the affected countries and bring the virus home, where they can infect others, for example, during sex. In the home countries, those mosquito species that pass on the virus are more likely to be excluded from major outbreaks. This is the case, for example, in Germany.

For affected regions, the health companies issue travel warnings for pregnant women. In addition, tourists should increasingly protect against mosquito bites, to prevent a Zika virus infection.

Zika virus infection: symptoms

A Zika virus infection is often asymptomatic, that is: carriers of the pathogen show no signs of disease. People with Zika virus infection are usually mild.

The first symptoms of Zika virus appear after about two to seven, sometimes only after twelve days (incubation period). The signs are similar to those of other viral diseases transmitted by mosquitoes, especially those of dengue or chikungunya fever. For example, sufferers usually suffer from the following symptoms:

• slight fever (“subfebrile” temperatures around 38 degrees Celsius)
• nodular-blotchy rash (maculo-papular exanthema)
• Joint pain (arthralgia)
• red eyes due to conjunctivitis (conjunctivitis)

Some patients feel very ill and severely beaten and also complain of headaches and muscle aches. Rarely, dizziness, stomach pain, nausea, vomiting and diarrhea are also reported. Serious illnesses, such as dengue (bleeding from massive platelet waste) or chikungunya (joint pain for months, bleeding), are very rare.

However, some doctors suspect a link between a Zika virus infection and possible diseases of the nervous or immune system. For example, after the outbreak on the French Polynesian islands, the incidence rate (incidence) of Guillain-Barré syndrome increased twenty-fold.

Zika virus infection in pregnant women

A Zika virus infection usually heals without consequences after a few days. Only the rash persists for about a week. If the Zika virus affects pregnant women, the pathogen can be transmitted via the blood to the child – even without the pregnant woman herself experiencing symptoms.

In that case, the development of the child can be massively disturbed. It then threatens a microcephaly. The children come with a too small (micro) head (-cephalus) to the world. Often, the brain is damaged and the affected child is mentally handicapped.

If a woman becomes pregnant weeks after a cured Zika virus infection, there is no longer any risk to the child. According to current knowledge, the Zika virus disappears completely from the body again.

Guillain-Barré syndrome after Zika virus infection

Zika virus infection can also have dangerous consequences for adult infections. In isolated cases, the infection causes Guillain-Barré syndrome. It is a rare neurological disorder that manifests as paralysis, which in the worst case may affect the respiratory muscles. About 20 percent of patients remain physically disabled, about five percent die.

Zika virus infection: causes and risk factors

In Zika virus infection, there are two important factors to consider: first, the presence of the Zikavirus itself and, second, its transmission to humans by Aedes mosquitoes.

Zika virus

The Zika virus belongs to the family of the so-called Flaviviridae and the genus Flaviviren. For example, this group includes tick borne tick-borne encephalitis (TBE) virus. Well-known other flaviviruses are dengue, West Nile and yellow fever virus. In a Zika virus infection, the single-stranded RNA virus infects body cells. How it penetrates exactly into the human cells and which processes follow, is still under investigation. As a rule, invading viruses use human cell components to proliferate.

Transmission of the Zika virus

The Zika virus is transferred to previous knowledge only by mosquitoes of the Aedes genus from person to person. Known representatives are Aedes albopictus (Asian tiger mosquito) and Aedes aegypti (Egyptian tiger mosquito), which can transmit, inter alia, the yellow fever, Chikungunya and dengue virus. The Zika virus multiplies after the sting in the human body. With renewed stitches, the mosquito picks up the pathogen again, transfers it to other people and thus spreads a Zika virus infection. Humans and primates are considered the main carriers of the Zika virus.

Among the dangerous mosquitoes is the Asian tiger mosquito (Aedes albopictus). It is about five millimeters small, black-silver-white striped and found in almost the whole world, which is why experts do not rule out a spread of the Zika virus to other countries, including Europe. In Germany in 2007 their eggs, in 2011 finally living specimens were discovered.

Zika virus infection during sex

The Zika virus can also be transmitted during sex – even if the transmitter has no symptoms (more). Especially men are transmitters, presumably because the virus manages to hide in the shielded area of ​​the testes longer before the immune cells. Male travelers from Zika regions should use condoms for at least eight weeks after they return home. By contrast, women probably transmit the virus during sex only in the acute stage of the disease.

Zika virus infection via blood

Also in blood transfusions theoretically the Zika virus can be found. A transfer in this way, however, is considered extremely unlikely and has been proven only in a few cases. Nevertheless, travelers returning from affected regions may not donate blood for a few weeks.

risk groups

As with all infectious diseases are multiple pre-existing (for example, high blood pressure, blood sugar disease, heart failure), immune-compromised and thus older people particularly at risk. Due to the increased occurrence of newborns with small heads (esp. In Brazil), especially pregnant women form a special risk group. However, the exact effects of Zika virus infection in infants still need to be explored. In children, the Zika virus infection is rather harmless as in adults.

Zika virus infection: diagnosis and examination

If you suspect that you have a Zika virus infection, there is no reason for particular concern. The disease is usually mild and sounds ineffective after a few days. However, if you have returned from a holiday or have had any other contact with someone who may be infected, you should always consult your family doctor or a specialist in tropical medicine. The symptoms of Zika virus also appear in other travel illnesses, which can have a much more severe course (for example, dengue). Even pregnant women will be advised to visit a doctor, since a Zika virus infection can cause damage in the development of the child (especially at the beginning of pregnancy).

There, the collection of medical history (anamnesis) is crucial. The doctor first asks for possible Zika virus symptoms. Above all, information about recent trips is important. The doctor may ask the following questions:

• Since when do you have complaints?
• When was the last time you were abroad?
• Where did you go and how long did you stay there?
• Were you stung by mosquitoes?
• Have you recently measured elevated body temperature?
• Have your symptoms abated in the meantime and are now increasing again?
• Do you have joint pain, red eyes or rashes?

After the detailed questioning, your doctor will examine you physically for a Zika virus infection. Among other things, he will measure your body temperature, palpate lymph nodes and examine the skin for possible rashes. He will also look after your joints and rule out other possible causes of joint pain. Eyes reddened provide the doctor with a crucial indication of conjunctivitis.

laboratory tests

To ensure the diagnosis of Zika virus infection, the doctor must take several blood samples. Some values ​​may be different from normal and more generally indicate infectious disease. For example, the number of white (leucocytes) and red (erythrocyte) blood cells and the amount of platelets (platelets) are determined. Especially the platelets typically fall off in Chikungunya and even more in dengue fever.

The genetic material of the Zika virus is detected for reliable detection. This is done using a special laboratory procedure called “reverse transcriptase polymerase chain reaction” (RT-PCR). The Zika virus RNA is thereby amplified and can be determined. In this way, the Zika virus infection can be secured within the first days after onset of symptoms. In addition, laboratory technicians can examine infected blood for specific antibodies to the Zika virus. These endogenous proteins of the immune system usually show up towards the end of the first week of illness.

However, these laboratory methods sometimes show incorrect results, as the substances used also react with other flaviviruses (cross-reactivity). In the so-called neutralization test, however, reliable detection of the Zika virus infection succeeds. However, this method takes several days and is very complex, which is why the faster and less expensive RT-PCR is the standard procedure.

Furthermore, up to two weeks after the first symptoms, the Zika virus can be recovered from the urine sufferer. Therefore, the Robert Koch Institute recommends always to send a urine sample to the laboratory in order to confirm a possible Zika virus infection even after some time.

Dengue fever, Chikungunya and other diseases

In the investigation of a Zika virus infection, the doctor tries to rule out other tropical / motion sicknesses. This is especially important because although a Zika virus infection is usually harmless, other diseases – but with similar symptoms at the beginning – can be significantly more complicated. The focus is on dengue and chikungunya. However, leptospirosis, malaria, rickettsial or alphavirus diseases (e.g., O’nyong-nyong, Ross river), rubella and enterovirus or parvovirus infections are also possible causes of the symptoms (differential diagnosis). 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 over 38.5 degrees Celsius
duration of fever	usually only a few days, two peaks with a fever break in between	one week	only a few days
spotty-nodular rash	often	Rare	often, lasting for about six days
Bleeding (hemorrhagic fever)	Rare	almost always	not known
joint pain	almost always and long lasting (sometimes months)	rare and if, of significantly shorter duration	yes, but also only a few days
Conjunctivitis	Rare	Rare	often

In addition, the white blood cells in Chikungunya are usually significantly more reduced than in a Zika virus infection or dengue. The platelets, however, fall in a critical area, especially in dengue fever. In Chikungunya their number is only slightly lowered, in a Zika virus infection, it is almost always in the normal range.

However, if you have typical Zika virus symptoms or other signs of illness during or after your trip, especially in high-risk areas, you should consult a doctor immediately.

Zika virus: treatment

A therapy that works directly against the Zika virus does not exist. Zika virus treatment is therefore limited to alleviating symptoms of the disease. Bed rest and adequate hydration are recommended as the body may lose a lot of water during the disease phase. Medications mitigate Zika virus symptoms such as pain (analgesics) and fever (antipyretics). For Zika virus treatment, doctors recommend acetaminophen (acetaminophen) to reduce the risk of bleeding.

Acetylsalicylic acid (ASA), which interferes with platelet function, should be avoided. If you have to take ASA because of other illnesses, ask your doctor for advice. For further symptoms of a Zika virus infection such as conjunctivitis, the treatment is extended accordingly.

Prevent Zika virus infection

The Zika virus can not be treated or vaccinated. In risk areas, it is therefore important to protect yourself from risky mosquito bites. Even those who are already infected should avoid further mosquito bites in the first week so that they do not get infected by these other people.

The following measures protect you from stabs:

Use insect repellent

Effective are so-called repellents with the active ingredients DEET, picaridine or IR3535. Plant-based experts recommend lemon eucalyptus oil or products based on it (PMD / citriodiol). Health authorities, however, advise against using repellents in babies less than two months old. To protect newborns from Zika virus infection as well, you should cover their bodies with clothing and use mosquito nets to equip pushchairs or seats.

Wear long pants and long-sleeved clothing.

For additional protection against mosquito bites and thus against a Zika virus infection you can spray your clothes with permethrin.

Watch out for mosquito nets, especially over the bed and windows.

This is particularly true during the day, as the Zika virus mosquitoes are particularly aggressive at this time. Again, you can better protect yourself from Zika virus infection by spraying the mosquito net with permethrin. Please note that high solar radiation cancels permethrin protection.

Avoid and eliminate watering holes.

Here mosquitoes multiply, which lead to a Zika virus infection. Empty water and dustbins regularly or cover places where new mosquitoes can ripen in the moisture (plant planters). Avoid living in close proximity to ponds or similar waterholes. It may be necessary to use insecticides.

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

Follow the current recommendations of the health authorities. For more information on the current state of Zika virus infections, visit the websites of the World Health Organization, the 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 high risk area. Tell your gynecologist about your trip no later than the next check-up. In case of illness you will be tested for a Zika virus infection and if necessary initiate further investigations. If you feel healthy, your doctor will use the information to pay particular attention to early signs of a defective brain and skull development in the child.

Not only with a Zika virus infection, but generally applies:

See a doctor immediately if you suffer from symptoms such as fever, red eyes, skin rash, nausea, headache and body aches, especially on or after traveling to high-risk areas!

Do not be afraid to visit clinics in your destination country if necessary. In this way, other, more severe diseases can be detected early and treated. Protect yourself well enough from mosquitoes in this time, so that the spread of a Zika virus infection can be contained.

Zika virus vaccination

A medical precaution against a Zika virus infection is not yet possible. However, the first promising studies are already in progress.

Zika virus infection: disease course and prognosis

The Zika virus infection often runs without signs of illness. Many infected people do not even notice that they carry the virus. If symptoms appear, the symptoms last only a few days to a week. It usually keeps the rash the longest. Treatment in the hospital is only necessary in exceptional cases. So far, little research, there are, however, first indications of possible complications.

Zika virus complications

microcephaly

The most dangerous complication of Zika virus infection affects unborn children. If the mother becomes infected, there is a risk of microcephaly. The heads of the affected children are abnormally small and their brains are also malformed, resulting in severe mental disabilities or even the early death of the child. This may also be the case if the mother had not noticed any symptoms of the disease.

Guillain-Barre Syndrome

For adults, the risk of Guillain-Barré syndrome increases after Zika virus infection. It is a neurological condition in which the nerves are inflamed due to misguided immune responses. The result is paralysis and sensory disturbances, which usually start at the legs and ascend towards the trunk. In the worst case, this can lead to respiratory paralysis and death.