Zika virus and the 2016 Olympic Games

A recent Editorial¹ in The Lancet Infectious Diseases used erroneous reasoning to argue that Zika virus poses no worry for the Rio de Janeiro Olympics—namely, that 92% of Zika cases are far away from Rio (wrong: Rio de Janeiro state has 29% of probable Zika cases, more than anywhere else in Brazil²); that campylobacter is more dangerous (irrelevant: so is dynamite); that just three known travellers were infected with dengue virus during Brazil's 2014 World Cup (glib: Brazil's ruinous Zika virus outbreak began with just one infected traveller³); and that worrying is pointless anyway because Zika virus is already found in dozens of countries (fatalistic: by that logic it would never be worth intervening to slow a disease's spread). Tastelessly the Editorial opens with a Nazi reference—the reductio ad Hitlerum seldom foreshadowing a wise analysis to come—and concludes with this: “Zika virus represents a minimal threat to games visitors”.

But how can anyone be so narrow minded to think only about games visitors? Actually Rio's Olympics are a risk to global health, for seven reasons.

First, the Olympics could not be better engineered to spread disease, because they attract visitors from every country in the world—something that no other mass gathering does, not even the World Cup. If visitors become infected, even asymptomatically, and return home to tropical countries having the right mix of Aedes aegypti mosquitoes and overladen slums, that could establish local viral transmission, and new outbreaks of microcephalic, brain-damaged children disabled for life.

Second, there are many places this outcome can eventuate. Africa and Asia have A aegypti and slums aplenty, and have long had Zika virus, but so far have mostly avoided the post-2013 neurotrophic strains of the virus that are ravaging Brazil.⁴ If even a few Olympic travellers introduce those newly evolved strains to those continents, riddled with weak health systems (weaker than Brazil), the outcome could be dreadful.

Third, although the estimated 500 000 Olympic visitors seem an inconsequential drop in the bucket of global travel, consequence has come from much less. Brazil's outbreak is hypothesised to have started with just one infected carrier travelling in 2013 from French Polynesia to the Americas.³ Not 500 000, but just 329 travellers entered Brazil from Oceania's small islands that year—suggesting that even a very small number of travellers can do damage, if they return to the right setting for the disease.⁵ Reasoning much like this, the US Centers for Disease Control and Prevention (CDC) now agrees that the Rio Olympics might put some low-income countries at “a unique or substantive risk [of] mosquito-borne transmission of Zika virus in excess of that posed by non-Games travel”.⁶

Fourth, WHO's advice on Zika virus and the Olympics is feeble. Unlike the CDC, which recommends that workers “consider delaying travel”,⁷ WHO advises both Olympic workers and tourists to carry on with mosquito repellent and condoms—useful, but half measures, as malaria or AIDS prove.⁸ WHO also suggests avoiding “impoverished and over-crowded areas [having] poor sanitation”—clueless that much of Rio fits that description.⁸ In a show of wishful thinking, WHO reasons that the Olympics pose “very low risk” because cool winter weather in Rio will suppress Zika mosquitoes.⁹ Gambling on Rio's weather is irresponsible, particularly this year when climatologists predict a 70% likelihood of above-normal winter temperatures, and just a 5% likelihood of below-normal temperatures.¹⁰ Yet those are the odds WHO is staking global health on.

Fifth, even assuming the Olympics have very low odds of spreading Zika virus globally, that is only half the issue, because if it eventuates, the outcome—new microcephaly outbreaks among children—will be major and devastating. History teaches that it is foolish to disregard low odds, high impact risks—eg, Chernobyl, Eyjafjallajökull, and Fukushima.

Sixth, there are alternatives. The Olympics could be delayed a year or two, pending proof (now lacking) that herd immunity in Brazil is effectively reducing incidence of Zika virus infection. Or the Olympics could be moved, like the 2003 Women's World Cup was as a result of severe acute respiratory syndrome (SARS) in China. That seems overdue, because Zika-linked microcephaly cases already exceed SARS deaths.

Last, one cannot forget health equity. Attending the Olympics is expensive. Those who can afford the panem et circenses are the global 1%, and although they do so freely and with informed consent about Zika virus, their poorer compatriots who are not travelling to Rio have no such autonomy, though they bear the greatest risk of microcephalic, brain-damaged babies should infection spread. Once harmed, not a penny of what is budgeted for the Olympics will go to salve or compensate those victims. Making excuses for this sour bargain, as The Lancet Infectious Diseases did, is to endorse a monstrous externalisation of risk, with indifference and inequity.