Zika outbreak occurring in Brazil since April 2015 seems to become a threat regarding the on coming Olympics Games in Rio de Janeiro. Scientific experts disagree on the opportunity to keep on going or to cancel the Games according to Public Health concern.
May be is nowadays the right timing to review objectively a more global risk assessment by including geo-localization and timeline.
What do you need to define an outbreak?
- one virus, Zika, circulating around a human reservoir;
- one vector, Tiger mosquito, Aedes aegypti or albopictus;
- temp > 18°C mostly raining season (hot and wet)
Meteo forecasts pour August 2016, with uncertainty, are pretty sunny and mild (25°C). Keeping in mind that Rio is in South Hemisphere and the season will be winter which is not the most convenient season for mosquito breeding.
Recently Brazilian MOH gave a statement on the Zika outbreak, noticing that it is decreasing following a peak on Frebruary with 16.059 suspected cases. Early May 2016, only 2053 were reported, 87% less…Nevertheless, WHO recommends pregnant women not to travel to Zika infected areas, including Brazil. WHO stated that Zika is causing microcephaly with fetus.
This statement, to be carefully taken for what it is and no more, is pointing out the population at high risk, I mean, young women of childbearing age or pregnant (mainly first quarter of pregnancy). As a reminder, 80% of Zika cases are without clinical symptoms which are more or less the same than for Dengue and Chikungunya. This, to focus on the usefulness of Zika testing.
There is still a debate surrounding Zika causing microcephaly as stated by US CDC and WHO. There are now evidence showing that Zika leads to auto-immune reaction which might help or contribute to neural cells of central nervous system defects. It is also important to review prevalence of microcephaly in Brazil, between 1 to 2/10.000 births as it is usual outside of Zika outbreak. By the way, these numbers are confirmed so far by epidemiological data coming from Colombia.
As of today, How could we conclude?
- Zika reservoir (and cases) is decreasing;
- The season will be Winter in Rio in August;
- At the same moment, In Europe and North America (Summertime) environmental conditions would be easy to help mosquitoes breeding and spreading to northern regions, previously unlikely exposed to Aedes albopictus.
- The main risk for Zika are pregnant women who are kindly invited not to travel to the infected areas.
- The prevalence for CNS defects including microcephaly is very low and close to the normal prevalence according to existing data (2012-2015), before Zika outbreak in Brazil.
At the end of the day, there are poor and few arguments to decide to postpone or cancel Olympics Games of Rio 2016. Simple mitigation or pre-emptive measures such as oral contraceptive and safe sex with condoms would be enough to control the risk exposure to Zika virus and contamination.