The recent news that four senior golfers have pulled out of the Olympic Games has received widespread coverage. The reason given for their boycott concerns fears over the Zika virus: as golfers spend perhaps more of their sport outside exposed to the elements, they may be at an increased risk of being bitten by a Zika-carrying mosquito than say a swimmer or a pole-vaulter. Even a marathon runner might be expected to only be outside for a few hours at most.
There is a body of opinion that would suggest that these worries are an over-reaction to the risk posed by this ‘new’ virus. They would cite that the Aedes mosquito, the insect responsible for the transmission of Zika, is less prevalent at present, as it is the Brazilian winter. Furthermore, they would point to the mass fumigation processes that have been said to be occurring in an attempt to control the mosquito population. Lastly, they would reiterate that it is only pregnant women that should be especially concerned about the Zika virus, as for others if symptoms are experienced at all, they are mostly of a mild flu-like illness from which people recover quickly and usually without complication.
Firstly, yes, it is winter in Brazil, but the average temperature is still a warm 28 degrees, still sufficient to support the life-cycle of the Aedes mosquito. Secondly, it is unclear at present how the widely publicised financial difficulties faced by the Rio state government will affect the fumigation processes, which are labour-intensive and therefore costly.
It is the last point - that it is only pregnant women who have anything to fear from the Zika virus - which is recently being questioned, however. As Zika has been found in the semen of affected males many weeks after infection has occurred, a raft of appropriate health precautions are currently being advised by official bodies (such as Public Health England and the CDC) that may make some men think twice about attending the Rio Games.
Although the precautions vary in the specifics, the essential feature is that if a male partner might have been exposed to Zika, the couple should pause trying for a family for fear of transmitting the virus to the foetus and risking life-defining abnormalities. The problem is this: as around 80% of infections in potential parents go unnoticed, unless the men have specific tests following their return home, they will not be certain that they have not been infected by Zika – and able to pass it onto their partners. A week’s competition (or visit to Rio) may mean months of condom-use after returning. In this context, the decision of the golfers may be more understandable.
It is true that the 500,000 people expected to attend the Olympics are dwarfed by the much larger figure of the yearly visitors to Brazil, which stands at 6 million. Therefore, a common opinion is that the number of Olympics visitors make an inconsiderable addition to all those potentially able to spread the virus abroad that visit Brazil at other times of the year. Whilst simple statistics may support this opinion, it may be worth considering whether the demographic of the Olympics attendees may allow for a greater global spread of the virus.
A interesting paper produced by the CDC has recently looked at the composition of the expected travellers to the Olympics, concluding that only if Zika were to be later found in four certain countries (Chad, Djibouti, Eritrea and Yemen) could it be reasonably surmised that the Olympics had definitely caused the epidemic to occur in these countries. These particular four countries were picked-out since their nationals rarely travel to Brazil during the year. Any Zika cases following the Olympics, it is argued, would be attributed to the infections brought back by the Olympics delegation or supporters from the four countries.
But perhaps this is not the most pressing issue. A more important consideration may be whether the Olympics will contribute towards global transmission, rather than irrefutably be said to start epidemics in new countries.
Transmission of the virus results when a Zika-infected patient, on returning home, is then bitten by local mosquitos that subsequently go on to infect others. This is called autochthonous spread. Only some countries will be permissive for such transmission, however. If visitors from the UK, for example, are infected there is little to worry about: the UK’s chilly shores do not support the Aedes mosquito; an outbreak of Zika will not occur there. Visitors from countries where such mosquitos are common, such as countries in Africa or Asia, have a much higher chance of establishing a home-grown outbreak of Zika. If more people from these countries travel to Zika-affected Brazil because of the Games, there is a higher risk of bringing the infection back home and establishing local epidemics. Whether the increased risk will result in actual cases is unclear, however. Time will tell.
DEET containing sprays should be applied and reapplied whenever going outside. Covering up to ensure little skin is exposed is wise, as is the use of air conditioning, room fans and bed nets, if available. Such precautions will not only help reduce the risk of Zika, but also prevent other prevalent mosquito-borne diseases, such as dengue fever, chikungunya, yellow fever and of course malaria. If Olympics visitors plan to travel outside of Rio for other sporting events, or just sightseeing, these preventative measures become even more important.
It should be borne in mind that travellers are much more likely to experience gastro-intestinal symptoms whilst travelling, and precautions such as drinking bottled water, eating properly cooked food, avoiding street food, and practising frequent hand-washing are wise. Together with avoiding mosquito bites and being adequately vaccinated in the first place, most travellers to the Olympics will be relatively untroubled by common infectious diseases. Those who are pregnant or wishing to become so, however, should still consider whether they should undertake a journey to the Olympics on this occasion.
Dr Simon Worrell, Healix International.