Francesca Tomasi received her B.A. from the University of Chicago and currently does microbiology research.
The summer Olympics will start in Rio de Janeiro on August 5th. Unfortunately, the Olympics are not the only thing Brazil is hosting this year: the country’s northeast region is the epicenter of the ongoing Zika pandemic. The first rounds of clinical and laboratory studies have finally been published, and they concretely establish a link between Zika and pediatric microcephaly, as well as other forms of brain disruption in adults. At this point, it is important to remember that Zika causes mild (if any) symptoms in the vast majority of people. Most individuals who become infected with the virus will not experience neurological effects; similarly, most pregnant women who contract Zika will not deliver babies with microcephaly. That being said, however, the fact that Zika can cause (and has caused) such devastating conditions in thousands of people means it must be taken seriously and prevention must be prioritized. It is similar to Rubella in this respect – Rubella does not severely sicken most of the people it infects, but it does have the ability to adversely affect fetuses. This is why children every year are vaccinated against Rubella; large-scale vaccination creates herd immunity, which prevents an outbreak of the highly-contagious virus from occurring. Furthermore, future mothers do not run the risk of contracting the infection while they are pregnant. Measles and mumps are even milder viruses that cause unpleasant rashes and next to no neurological effects. Measles and mumps have not been linked to placental transmission but can be dangerous to newborns or immunocompromised children. As a result, vaccination of children against measles and mumps is listed as an essential immunization by the WHO. Case in point: Zika, too, causes a mild disease that can have severe outcomes in a subset of individuals. Thus it should be taken seriously the way measles, mumps, and Rubella are. The main difference is that Zika is spread by mosquitoes rather than from human-human contact, which makes it both easier and harder to control. We also do not have a vaccine yet, so additional preventive measures must be taken in the meantime.
As of May, 2016, Zika has spread to over 50 countries. Additionally, the World Health Organization recently announced that Zika is likely to spread to some parts of Europe by the end of spring. This announcement is based on a risk assessment that pooled together public health, climate, and mosquito data for each of the 53 member states in the European region. Regional dengue fever transmission was determined to be a good statistical precedent for Zika transmission as well, since the two viruses are related and transmitted by the same mosquito. Flocks of tourists and athletes traveling between Europe and Brazil for the Olympics, as well as to other parts of the world for summer vacation, are bound to give Zika plenty of opportunities to migrate over to Europe and any other currently naïve regions. For these reasons – and more specifically, that the country bearing the brunt of the outbreak is hosting the 2016 Olympics – many have argued in favor of canceling the Games or at least changing the Olympic venue. At least half a million people are expected to travel to Rio this summer. Back in January, the International Olympic Committee announced that Rio would be a “safe environment” for the Games, despite the spread of Zika in other parts of Brazil. However, in the past few months, data on just how many people are infected have been coming in. Not only is there Zika virus in Rio de Janeiro, but the virus’s incidence rate there is the fourth worst in Brazil at 157 per 100,000 people.
A counterargument to a feared spike in Zika cases in Rio is that Brazil is not in the Northern Hemisphere. So while it will be hosting the Summer Olympics this year, Rio will actually be doing so during its winter. This could mean a plummet in the local mosquito population due to cooler, dryer temperatures. Going back to the dengue surrogate for Zika, previous reports have shown that Brazilian dengue rates have in fact tended to peak in March and wane during the winter. Wane, however, is the operative word: dengue is not strictly seasonal the way the flu is; the flu spikes in the winter and virtually disappears in the summer. Dengue, however, can be very prevalent during the summer, and a little bit prevalent during the winter. In addition, despite these historical trends, Rio de Janeiro is actually currently facing an alarming rise in dengue cases, adding insult to the injury brought about by Zika. This news is coming despite Brazil’s biggest military mobilization in history: 220,000 members of the military and 315,000 public officials have been deployed to wage war against Aedes aegypti.
Half a million people converging into somewhat of a hot zone and then diverging back out to their respective home countries is an epidemiologist’s (and overall public health) nightmare. Of course, not all 500,000 foreigners are going to become infected with the virus. But if we take the current per capita estimate of Zika in Rio de Janeiro and apply it to the imminent tourist influx, we can reasonably expect at least 800 tourists to become infected (assuming the outbreak does not wane in the Brazilian winter, parallel to what seems to be happening with dengue this year). The numbers could be lower if people are vigilant about mosquito repellent, but they will not be zero.
Epidemiologically, it takes one infected individual to spark an outbreak: the Ebola epidemic in West Africa two years ago, for instance, started from a single “patient zero,” an infected toddler. Phylogenetic analysis (inferring evolutionary relationships between different samples to trace an organism or virus’s history) of the current Zika outbreak points to a single viral introduction in the country some time in 2013. Eight hundred infected travelers offer 800 opportunities for Zika to infiltrate a new pocket of the globe. Many infections in these pockets could be inconsequential – consider an Olympic spectator flying back to Norway, where one would be hard pressed to find a single Aedes mosquito – but others could be more significant in regions that harbor abundant Aedes aegypti and possibly Aedes albopictus.
Given the highly-interconnected nature of today’s world, Zika will inevitably spread wherever it can at one time or another. Such are the laws of networks (see: the world-wide spread of HIV, flu, and tuberculosis). Bringing together hundreds of thousands of people from all walks of life near the epicenter of an outbreak, only to send them back home after a few weeks, will only speed up the process, as one editorial describes. It is for this reason that some people are calling for the Olympics to be postponed, or at least for the venue to be changed. This has been done in the past with athletic events – this year, for instance, US baseball league games have been rescheduled and transferred out of Puerto Rico due to fears of Zika. In 1976, the Winter Olympics were moved from Denver, Colorado, to Innsbruck, Austria (for an entirely different environmental reason, but it happened). Furthermore, multiple ex-Olympic venues still have working facilities that could be used for the summer Olympics (London, Beijing, Athens, and Sydney). Both logistically and financially, this is not going to happen. But would it have happened if there have been serious conversations half a year ago?
Interestingly, the people talking about Zika in the context of the Olympics for the most part are not those directly involved with either the Games or the virus: the International Olympic Committee and the World Health Organization. One member of the Olympic committee went so far as to dismiss Zika as bogus: “If you are a young woman who is pregnant, and not many athletes will be, or planning to get pregnant, then there are precautions you should take. Beyond that, for me it’s a manufactured crisis,” said IOC member Dick Pound. Mr. Pound’s culpabilities are two-fold: for one, the majority of people flocking to Rio for the Games will not be athletes but rather friends, family, coaches, staff, and fans. Mr. Pound’s one-sided approach, only to consider the athletes in this crisis, goes against the Olympic mantra of universal respect and ethics. Furthermore, Mr. Pound is denying the concrete science of Zika’s potential (albeit rare) pathological consequences.
The World Health Organization was commendably quick to declare Zika a Public Health Emergency of International Concern, inciting the mobilization of medical and research institutions. The US Senate has approved a $1.1 billion measure to fight the virus (though people are calling for all of the originally requested $1.9 billion), and many other countries are rallying forces, including Brazil’s epic military mobilization. The WHO and CDC have issued travel advisories and recommendations for women planning on becoming pregnant, going so far as to advise that at-risk women postpone conceiving children until the virus is fully understood or the outbreak controlled. The National Institutes of Health and many other institutions are hard at work researching the virus and trying to find rapid diagnostics, treatments, and vaccines.
On Tuesday, the WHO issued a statement that the Olympics should not be postponed or moved. Margaret Chan, director-general of the WHO, said the decision came from the notion that "[y]ou don't want to bring a standstill to the world's movement of people. This is all about risk assessment and risk management." She then added that visitors to the Games should ensure that they wear adequate mosquito protection and that pregnant women should avoid travel to Brazil altogether. She did not address the specific risk assessments that went into this statement, specifically the epidemiology of bringing individuals (pregnant or not) somewhere they will soon leave and possibly take the virus with them. There are also other public health concerns about an Olympics in Rio, independent of Zika: for example, grimy water will undoubtedly affect rowers, sailors, and even some swimmers. In the case of Zika, most people have nothing to worry about. However, that should not justify knowingly increasing the speed with which the virus can spread. And what has the IOC done about contaminated water?
Interestingly, the IOC was ready to postpone or reschedule outdoor events in Beijing in 2008 due to concerns about smog. Air pollution is a public health threat that the IOC took seriously because of its direct impact on athletes. However, since Zika virus is probably not going to be a threat to most of the athletes competing (though the filthy waters will be for many), is it still the IOC’s responsibility to at least seriously address the virus and the Olympics’ location in tandem with other public health concerns? Yes. The Olympics are not exclusively about the athletes. The Olympics are supposed to be a symbol of, as China put it in their slogan 8 years ago, “One World, One Dream.” They are supposed to be “a chance…to come together as a human family for something.”
Of course, the Olympics will not be canceled, postponed, or relocated. They are barely 2 months away, and Brazil is surely gearing up for an incredible show. The country is also clearly working hard to control mosquitoes, between mass spray-downs and air conditioning unit installments to ward off the bugs. There are ways for travelers to prevent mosquito bites: that, often coupled with prophylaxis, is why travelers rarely contract malaria, dengue, and other tropical mosquito infections. Furthermore, the most at-risk individuals (pregnant women) have been advised to avoid travel to Brazil and other Zika-bearing nations. Nonetheless, the Olympics will surely facilitate the spread of Zika to new countries, and the IOC has been a little sloppy about responding to this. Its communication and reaction to the public health concerns surrounding this year’s Games could have been better. For now, however, we can get excited about some great athletics. Meanwhile, travelers should also be aware of the role they are capable of playing in the spread of Zika and how to minimize it.