The global spread of the Zika virus continues, and up to 2.2 billion people could be at risk during the warmer months of the year. Brazil alone has at least 1.5 million cases to date, alongside around 1,000 cases of Zika-related microcephaly – babies born with abnormally shrunken brains. Just recently, the link between the virus and neural cell death was confirmed by both a landmark experimental study and by the U.S.-based Centers for Disease Control and Prevention (CDC).

With no vaccine and no signs of the epidemic slowing down, health officials are deeply concerned. In an opinion piece for the Harvard Public Health Review publication, Dr. Amir Attaran, a lawyer, biologist and law and population health professor at the University of Ottawa, addresses the rather sizable elephant in the room: The upcoming 2016 Olympic Games in Rio de Janeiro, the state with the highest numbers of Zika infections in the country.

He argues that, although it would be costly for the government, the Games must not go ahead, as it will provide the Zika virus with a globally diverse, mobile, enormous crowd to infect. It’s unlikely that the Games will be cancelled, however, so a public health catastrophe may be imminent. “According to the Brazil’s official data, Rio is not on the fringes of the outbreak, but inside its heart,” he writes.

^{The risk of microcephaly jumps dramatically if the mother is infected with Zika. Mario Tama/Getty Images}

Hopes for the disappearance over the current Brazilian winter – which extends into the start of the Games – are also dashed by Dr. Attaran: “If one assumes, reasonably, that Zika will behave like dengue fever, because they are caused by related viruses and transmitted by the same Aedes aegypti mosquito, then Zika transmission will ebb but not vanish in Rio’s winter, just as dengue did in winters past.”

Around 7.5 million tickets for the Rio Games are available, with about 500,000 visitors expected from abroad, according to the BBC. Add to that the hundreds of thousands of people working at the Olympics themselves, and of course the 16.46 million people in the state of Rio itself, and you’ve got a lot of potential people to infect.

Richard Budgett, medical director for the International Olympic Committee (IOC), responded to Attaran’s statements, saying: “The clear statements from WHO that there should be no restrictions on travel and trade means there is no justification for canceling or delaying or postponing or moving the Rio Games. The IOC will continue to monitor the situation very closely and work with the WHO, and we're confident as we've been advised by the experts that the situation will improve over the next three months."

Although for most the infection appears to be harmless, it can cause serious neurological birth defects if passed on to a pregnant woman, either through a mosquito bite or sexual activity. Disconcertingly, a recent study showed that up to 29 percent of Zika-infected pregnant women had fetuses with severe abnormalities.

As the recent experimental study demonstrated, and as mentioned in this special commentary, the Brazilian strain of the Zika virus appears to be more harmful than the others found around the world. One study focusing on French Polynesia – the origin point for the current Brazilian Zika strain – revealed that if a fetus is infected by this strain, the chance of developing microcephaly increases by 53 fold.

Adults aren’t immune to neural cell death either, it seems: Those infected by Zika go on to suffer from Guillain-Barré syndrome, wherein their own immune system begins to attack nerve cells.

^{Efforts are underway to target the main vector of the disease, the Aedes aegypti mosquito. Torres Garcia/Shutterstock}

“All it takes is one infected traveler,” the researcher notes. “Brazil’s cataclysmic outbreak stems from a single viral introduction event likely between May and December 2013. A few viral introductions of that kind, in a few countries, or maybe continents, would make a full-blown global health disaster.”

He points toward the International Olympic Committee’s statement that the Games, among other things, are meant to foster social and ethical responsibility. “But how socially responsible or ethical is it to spread disease?” Attaran asks.