22 July 2016 - PRESS RELEASE

Zika Virus: are athletes and visitors of the Brazil Olympic Games at risk?

In June, the World Health Organisation (WHO) decided that the Olympic Games in Rio de Janeiro can take place despite the Zika virus. The risk of a further international spread is low. The virus is suspected to cause foetal damage and brain malformations during pregnancy. Experts at the German Center for Infection Research (DZIF) Prof Christian Drosten and Prof Jan Felix Drexler, University of Bonn, assess the situation.


Aedes aegypti mosquito: a vector for the transmission of Zika virus© cdc/James Gathany

How high is the risk for athletes and visitors of getting infected with the Zika virus at the Olympic Games in August and September?

There certainly is a risk of getting infected with the virus at the Olympic venues. However, the general activity of the transmitting mosquitos should decrease slightly with the start of winter in the southern hemisphere. Additionally, very many people in Brazil have already been infected with the virus and are therefore highly likely to be immune. For this reason, the chances of mosquito-to-mosquito transmission of the virus, and the rate of new infections in humans, will decrease with the decreasing rate of infection in mosquitos. In most cases, an infection with Zika is harmless, at most causing mild symptoms, such as conjunctival redness, headache and a general feeling of fever and fatigue. In contrast, the risk of infection with other diseases transmitted by mosquitoes, such as dengue and chikungunya viruses, which can cause severe symptoms, still persists. Brazilian authorities have taken far-reaching measures to fight mosquitos at the Olympic Games.

How can I best protect myself against mosquitos?

The mosquitos which transmit the above mentioned viruses are active during the day. Therefore, using mosquito nets at night as well as wearing long clothing that covers sensitive areas such as ankles, the neck and lower arms is recommended for protection. When using mosquito repellents, care should be taken make sure that the repellents are also recommended for use in tropical regions.

Can pregnant women travel to the Olympic Games in Brazil?

The exact risk of damage to the unborn child through Zika virus infections is still unclear. However, the current state of data strongly suggests that early pregnancy is the most likely period of time in which damage can occur. Pregnant women in the the first six months of pregnancy who cannot avoid travelling to a Zika region should therefore take special precautions to protect themselves against mosquito bites. The affected areas include the upcoming Olympic Games venues. Business travel related to the Olympic Games, where the traveller is mainly in air conditioned rooms (hotels, conference rooms, etc.), can be considered high personal protection.

How high is the risk of participants taking the virus back home after the Olympic Games? How long can they transmit the virus, e.g. to their partners?

When considering the risk of the virus being transmitted in Germany, two different situations have to be taken into account: firstly, the virus can be transmitted by men via semen over a long period of time, in individual cases even over several weeks. If there is no pregnancy, an infection passed on in this way will, however, not be more dangerous than a harmless infection transmitted by mosquitos per se. Condoms protect against this form of transmission. Men returning from a Zika region who are worried about infecting their pregnant partners can get tested with a specific antibody test about ten days after leaving the region. A negative test result rules out infection.

A further concern is the potential spread of the virus through local mosquitos. Although, up to now, no scientific data on the possibility of transmission though local mosquitos exist, this theoretical possibility cannot be ruled out with absolute certainty. If local transmission were to occur, it would certainly be very limited regarding time and place.

Should all people returning from a Zika region do a test to be sure?

A laboratory test should only be done in situations in which an unnoticed infection could have severe consequences. These include only a few cases. Examples are pregnant women, including those with a later confirmation of pregnancy, as well as men with pregnant partners who could get infected through sexual contact. Furthermore, patients with underlying diseases of the immune and nervous system, who are consequently at a higher risk of viral central nervous system infections, are also affected.


Zika virus
The Zika virus causes fever, rashes, joint pain and conjunctivitis. The virus can be transmitted to the foetus during pregnancy, which is assumed to be rare. Researchers suspect a link between the infection with the virus and brain malformations in babies: since October, an increase in the number of babies and foetuses with microcephaly, an abnormally small head, have been registered in Brazil. To date, it is unknown how frequently an infection during pregnancy causes such malformations. According to the current state of knowledge, the virus is especially transmitted by the mosquito species Aedes aegypti—a type of mosquito which does not exist on the European continent. The virus was first described in Uganda almost 40 years ago.

Virus research at the DZIF

The DZIF research field “Emerging Infections” has put in place an excellent foundation to enable rapid development of diagnostic agents, vaccines and antiviral drugs in the event of novel virus outbreaks, and to prevent further spreading of outbreaks. Christian Drosten’s research team in Bonn has already developed a standard test for the MERS pathogen which is being used worldwide. They are also involved in Ebola research.

Further information on the Zika virus provided by the Robert Koch Institute (in German): www.rki.de/DE/Content/InfAZ/Z/Zikaviren/Zikaviren.html

Travel information for the Olympic Games (in German):

Recommendations for Zika diagnostic testing are also provided by the Bernhard Nocht Institute for Tropical Medicine:


Prof Jan Felix Drexler/Prof Christian Drosten
DZIF research field “Emerging Infections”
University of Bonn

T +49-228-287-11697/+49-228-287-11055
E-Mail Drexler
E-Mail Drosten

DZIF Press Office
Karola Neubert und Janna Schmidt
T +49 531 6181-1170 und -1154

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