Polymarket’s hot new bet: Hantavirus

Over the past four days, bettors on the prediction platform Polymarket have wagered nearly $3 million on whether we’ll see a hantavirus pandemic this year. A cluster of cases of a particularly deadly strain of the virus erupted on a cruise ship last month, killing three people out of eight suspected cases linked to the vessel. Though the news has stoked fears, the World Health Organization currently classifies the risk of a full-blown pandemic as low. 

But Polymarket users are spending big across several hantavirus-related propositions—including whether a vaccine will be developed this year and whether or not officials will tie the cruise ship outbreak to a “lab leak.” Polymarket declined to comment on hantavirus betting. 

“I want to be unequivocal here. This is not the start of a Covid pandemic,” said Maria Van Kerkhove, director of epidemic and pandemic management at the WHO, at a Thursday press conference. “This is not Covid, this is not influenza. It spreads very, very differently.”

Because outbreaks of this hantavirus strain have occurred before, infectious disease experts already know that the virus requires close contact to spread between people, and a person with the virus is only infectious for about a day. Just as those metrics allow public health officials to calibrate their response, they also inform how some online gamblers are placing their money.

Online gambling has been on the rise since sports betting was legalized by the Supreme Court in 2018, but the Covid pandemic gave it a huge boost. In 2020, sports betting revenues jumped up 69 percent over the previous year, though not too many sports events were happening.

But there were other bets to be placed, like how many people would die from Covid-19, a topic some people wagered on as early as April 2020. At the time, those bets were illegal, the subjects of online betting being more strictly regulated. But a 2024 court ruling took the rails off of websites known as prediction markets. Now, on mega-platforms like Polymarket and Kashi, users can bet on almost anything—including public health crises.

“Anybody who’s betting on a viral spread, I’m going to…guess that they have an addiction problem when it comes to gambling,” says John W. Ayers, a public health professor at University of California, San Diego. “If someone is very addicted to gambling, they’re more likely to find themselves interacting with these more fringe things you could possibly bet on.”

For several years, public health experts have been concerned that gambling addictions are on the rise, though the exact numbers are hard to pin down. A study Ayers led that came out last year found that Google searches seeking help for gambling addiction jumped 23 percent nationwide since the legalization of sports betting. Other researchers estimate about 10 percent of men ages 18 to 30 have a problematic relationship to gambling. 

Platforms like Kalshi and Polymarket grow based on use, helping the range of niche bets to multiply—and since taking off during the Covid pandemic, the prediction-market industry has multiplied in size many times. By 2030, it’s been estimated, prediction markets could  grow to $1 trillion in annual trading volume.

That gambling is a public health issue in itself, Ayers says. Gambling addiction is correlated with other forms of addiction that are significant sources of premature deaths in the US. Financial stress isn’t great for your health, either. 

“Culturally, it’s normalized, and now we give it this veneer of, ‘Oh, it’s not gambling. It’s a prediction market.’ Doesn’t matter,” Ayers says. “The harm still exists. Call it a prediction market or a sports book, you’re still losing money, and the house always wins on these bets.”

Unlike many other forms of addiction, gambling problems can often be invisible before someone hits rock bottom, especially now that most of these transactions are happening in an app. It is possible to regulate prediction markets and place barriers on addictive behaviors—some countries place limits on how many bets a person can take, restrict the use of credit cards, or institute mandatory rest periods between bets—but right now, the US more or less doesn’t. Instead, we bet on everything: viruses included.

“The fact that people will gamble on these things indicates to me the larger societal problem—everything becomes an opportunity for monetization,” Ayers says.

Or as Donald Trump put it earlier this year, “the whole world, unfortunately, has become somewhat of a casino…it is what it is.”