[This article is written by Adelaida Sarukhan (ISGlobal) and Jose Muñoz (ISGlobal-Hospital Clínic) and it has been published in Spanish in El País - Planeta Futuro ]
Over the last few days, Zika has again become the focus of debate, regarding the risk of going ahead with the Olympic Games in Brazil. In the first place, it is important to distinguish the risk to the athletes’ and tourists’ individual health, from the risk to public health.
What is really at stake here is a global health issue
For the athletes, official delegates, and tourists, the risk to their health is very low given that Zika virus infection causes mild symptoms (rash, fever) that last only a few days. Some adults have developed a neurological syndrome (Guillain-Barre Syndrome) although this seems to happen at an extremely low frequency. The main threat posed by Zika virus is for pregnant women, whose foetus can suffer neurological malformations (including microcephaly) if the virus crosses the placenta.
The key question is it will favour the spread of Zika virus towards other countries where the vector (Aedes aegypti) is present but there is no ongoing transmission
What is really at stake here is a global health issue. The key question is whether going on with the games as planned will favour the spread of Zika virus towards other countries where the vector (Aedes aegypti) is present but there is no ongoing transmission of the Asiatic lineage of the virus that is currently circulating in Latin America and has been shown to cause foetal malformations. These countries include the African continent, USA, a great part of Asia and the Mediterranean Basin (where there is no Aedes aegypti but its cousin the tiger mosquito or Aedes albopictus is present).
The arguments in favour of postponing or changing the site of the Olympic Games were recently summarized in an open letter signed by more than 150 academicians. The reasons they give are the following:
- Rio de Janeiro is highly affected by the virus (it has the second-highest number of cases in the country).
- Although the Games will take place in winter, when there are fewer mosquitoes, this year has been hotter and the number of cases of other mosquito-borne diseases (dengue) has increased as compared to the same period last year.
- Because of its neurotrophic nature (i.e. its capacity to infect nervous system), it is plausible that the virus may cause other yet undiscovered neurological injuries.
- A percentage of the estimated 500,000 visitors will return infected to their home countries in the Northern hemisphere, when mosquito activity is at its highest. If this occurs in countries with fragile health systems (Southeast Asia and Africa) the impact could be even greater.
- Finally, the authors argue that other sporting events have been moved or cancelled in the past for public health reasons: the Women’s World Cup in 2003 due to SARS and the Africa Cup of Nations due to Ebola.
Or not to postpone?
In reply to the letter, the WHO has declared that cancelling or changing the location of the 2016 Olympics will not significantly alter the spread of Zika virus.
- The main argument for this is that the Olympic Games in Brazil account for only a small fraction of the total travel to and from the 60 countries and territories (39 of them in Latin America) with ongoing virus transmission. Along the same line, the CDC in US has declared that the number of travellers to Rio represent less than 1% of the total of travel in regions affected by Zika.
- Cancelling or postponing the Games would give a feeling of false security with regards to the globalization of the disease.
- The athletes and tourists will lodge in conditions that are less favourable to mosquito bites (hotels in zones with proper sanitation, air conditioning, etc.)
- August is the dry season and the number of mosquitoes will be lower. Besides, the local authorities have launched aggressive fumigation campaigns in the zones where the Games will take place.
- The best way to reduce the risk of spreading the virus to other regions is following the public health recommendations: avoid mosquito bites, avoid travel to regions with active transmission if pregnant, and practice safe sex during 8 weeks after returning (or 6 months in case of experiencing symptoms).
The WHO is and should continue being the worldwide reference in public health
It may also be important to assess the impact of other past events. For example, the Rio Carnival that took place last February attracted more than 1 million visitors (one fifth of them were foreigners) but does not seem to have had a major impact on Zika virus spread. During the Brazil World Cup in 2014, experts worried about the risk of dengue infection in tourists. However, a study published in Lancet in 2015 concluded that there were few cases (it is also true that it was a very dry year and with fewer mosquitoes).
At the end of the day, only the Brazilian authorities and the International Olympic Committee can take a decision on whether to cancel or change the date or site of the Games. Although severely criticized for its lack (or excess) of response to previous outbreaks (Ebola or H1N1 influenza), the WHO is and should continue being the worldwide reference in public health.
From the beginning of the Zika epidemic, WHO has coordinated the international response and has worked hand in hand with the Brazilian Government and the Olympic Committee. We trust that the organization will continue to monitor the situation, as promised in its last statement, and will be capable of updating its advice if necessary.
Adelaida Sarukhan is PhD in Immunology and a scientific writer at the Barcelona Institute for Global Health (ISGlobal).
Jose Muñoz is Assistant Research Professor at ISGlobal and head of the Tropical Medicine and International Health Service at the Hospital Clínic.
The Million Dollar Question: When Will We Have a Vaccine Against the Zika Virus?
Zika Virus: 10 Key Questions and Answers
Zika Virus in Europe: Alert Does Not Mean Alarm
ISGlobal Gets Involved in the Zika Response