Zika virus


Since May 2015 the Zika virus has been spreading spectacularly around the globe. Although its effects are usually mild, the infection can occasionally lead to serious neurological complications (microcephaly and Guillain-Barré syndrome).

Pathogens and transmission

Zika virus is transmitted to people primarily through the bite of an infected Aedes species mosquito (primarily Aedes aegypti but also Aedes albopictus). It can also be passed through sexual contact, and pregnant women who are infected can pass the virus on to the foetus. Zika virus has also been found in mother’s milk and in saliva, although there has been no proof so far that it can be transmitted through these bodily fluids. It could theoretically be transmitted via a blood transfusion, but so far there is no firm evidence of this.


In 60% to 80% of cases the infection is asymptomatic. In the other cases there may be a variety of clinical symptoms. The symptoms
generally disappear by themselves within four to seven days. There is no specific drug for treating the disease itself, so only the symptoms are treated.

Distribution and frequency

Until 2014 the disease occurred sporadically in around 20 countries in Asia, Oceania and Africa. Since May 2015 when the epidemic in Brazil started, 60 countries and territories in South and Central America, the Caribbean, the Pacific, Asia (Malaysia, the Philippines, Singapore, Thailand, etc.) and Africa (Cabo Verde and Guinea-Bissau) have been affected. The first reported cases of local vector-borne transmission of Zika virus in the United States came at the end of July 2016 from Florida (mainly from Miami-Dade County); by the end of October 2016 the figure had increased to more than 100. So far no cases of local vector-borne transmission have been reported in Europe. On the other hand, since November 2015 more than 1,700 cases have been imported to Europe from epidemic and endemic areas.

You will find more information on the pathogen on the site “Zika virus”


There is no specific drug for treating the disease itself,
so only the symptoms are treated. So far the main measure for preventing infection has been protection from mosquito bites, both indoors and outdoors. It is recommended to wear loose-fitting, long clothes treated with insecticide, use an effective repellent during the day and night, and to sleep under a mosquito net (especially in rooms without air conditioning).

Pregnant women, people with a weakened immune system or other chronic conditions, and those travelling with small children, should consult a doctor to find out about all the health risks associated with tropical diseases.


Under the terms of 5 May 2015 amendment to the ordinance on epidemics, samples from pregnant women must be sent to a national reference centre. For Zika virus this is the reference centre for newly emerging viral infections (NAVI/CRIVE) in Geneva (see link below).

Last modification 16.11.2018

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