Prediction Markets See Nearly $9M in Wagers on 2025 US Measles Case Totals

Nearly $9 million have been bet on future measles cases in the US on prediction markets Kalshi and Polymarket since January. There is some evidence that the measles predictions on Kalshi and Polymarket are accurate enough to be useful for modelling its spread. Prediction markets involve buying and selling shares related to an outcome with the cost of a bet determined by the way others have bet.

If 86 per cent of wagers on a given future event are “yes” bets, the cost of a “yes” share is 86 cents. If the event occurs, successful gamblers receive $1 for every share bought. The idea of prediction markets emerged from scientific research in 1988.

In 1988, Robert Forsythe, George Neumann and Forrest Nelson at the University of Iowa developed prediction markets to forecast US federal elections. In 2003, Philip Polgreen at the University of Iowa asked the economists to incorporate diseases into the prediction market. These markets were “in the spirit of education and public good,” Philip Polgreen said.

Prediction markets have turned commercial through companies including Kalshi and Polymarket. Kalshi and Polymarket are legal in the United States and regulated by the Commodity Futures Trading Commission. In February, a trader pseudonym Magamyman won $553,000 on Polymarket by correctly predicting when Ayatollah Ali Khamenei would be removed from power.

Khamenei was killed on 28 February 2026. Measles cases and outbreaks have been rising across the US. In June 2025, prediction markets favoured an outcome of around 2000 measles cases by the end of the year.

There were actually 2288 measles cases by the end of 2025. “I’ve seen many worse forecasts from our models,” Spencer J. Fox said. Spencer J. Fox at Northern Arizona University forecasts covid-19, influenza and RSV.

Measles is a disease that isn’t typically covered by scientific forecasting because the disease is “very probabilistic,” Spencer J. Fox said. ” Even so, prediction markets do not incorporate as many distinct forecasts as scientific models or offer as much granularity in terms of possible future outcomes.

“You would have to make 1000s of bets a week for all of the different forecasts that we’re making,” Spencer J. Fox said. He also said only experts can predict rare events. “If we don’t invest in the expertise for forecasting infectious diseases now, we’re going to be caught flat footed for the next covid-19,” Spencer J.

Fox said. Kalshi and Polymarket did not respond to New Scientist’s request for comment. @NewScientist reported that epidemiologists use multiple data streams including vaccination rates, genomic and climate data when forecasting diseases, and are constantly on the lookout for new data streams.