$9 Million Bet on US Measles Forecasts in Prediction Markets Since January 2026

Users have wagered nearly $9 million on predictions of future measles cases in the US via platforms Kalshi and Polymarket since January 2026, @NewScientist reported. These prediction markets allow users to buy and sell shares related to outcomes of future events, offering yes or no options.

The cost of a yes share is determined by the percentage of yes bets; for instance, if 86 percent of wagers are yes, a yes share costs 86 cents.

Successful gamblers receive $1 for every share if the event occurs. Kalshi and Polymarket operate as commercial prediction markets that are legal in the United States and regulated by the Commodity Futures Trading Commission. These companies are legal in the United States and are regulated by the Commodity Futures Trading Commission, but they face growing backlash from federal and state governments.

The concept of prediction markets originated in 1988 when three economists at the University of Iowa—Robert Forsythe, George Neumann, and Forrest Nelson—developed the idea to forecast US federal elections.

In 2003, Philip Polgreen, an infectious disease researcher at the University of Iowa, incorporated diseases into these prediction markets. “These markets were “in the spirit of education and public good””, says Polgreen. Prediction markets have shown accuracy in some measles forecasts, though they complement rather than replace expert models.

In June 2025, these markets forecasted around 2000 measles cases in the US by the end of 2025. There were actually 2288 measles cases in the US by the end of that year. Epidemiologists use multiple data streams, including vaccination rates, genomic data, and climate data, to predict diseases.

Measles is a disease that isn’t typically covered by scientific forecasting because it is very probabilistic, says Spencer J. Fox. Prediction markets harness the wisdom of crowds, and amateurs bring cognitive diversity that replaces what they lack in expertise, says Emile Servan-Schreiber.

Companies like Kalshi and Polymarket have expanded prediction markets beyond their academic roots, allowing bets on various events, including diseases. This commercial shift builds on the foundational work from the University of Iowa, where small wagers on elections proved accurate.

Polgreen collaborated with the economists to adapt the markets for infectious diseases, aiming to serve educational and public purposes.

Over time, these platforms have attracted significant betting volumes, as seen in the recent measles wagers. The accuracy of past predictions, such as the close match between the 2000-case forecast and the actual 2288 cases in 2025, suggests potential value for disease modeling. Fox noted that while prediction markets offer a new data stream, they do not replace comprehensive scientific models.

Servan-Schreiber emphasized the role of diverse participants in enhancing forecast quality through collective intelligence. Despite regulatory oversight, these markets continue to operate, drawing bets on probabilistic events like measles outbreaks.