Rising CDC count leaves traders expecting U.S. measles cases to reach 6,500 this year

Traders now consider it likely that the CDC's count of confirmed U.S. measles cases will reach 6,500 or more in 2026, a clear step up from a toss-up when the story began.

The likely reason is the CDC's latest weekly update. On Oct. 30, the agency put the count at 4,852 confirmed cases through Oct. 29, an increase of 264 from the previous week, according to the CDC and Reuters. The larger weekly jump brought the total closer to 6,500 but did not reach it, leaving 1,648 cases to go.

Across the range of possible year-end totals, traders expect about 6,800 cases, with most of their bets falling between 5,900 and 8,600. That central figure has risen from about 6,550 when the story began. The likeliest range is 6,500 to 7,500 cases. Passing 6,000 is seen as likely, reaching 7,500 as unlikely, and 10,000 or 12,500 as long shots. Expectations for 10,000 have eased slightly.

The path has been bumpy. Bets on 6,500 climbed from Oct. 20 to Oct. 22, when passing the mark looked likely. They fell sharply on Friday, Oct. 23, and again on Monday, Oct. 26, dropping below even. They hovered around a toss-up through Oct. 30, then rose on Sunday and held most of that gain Monday. Reporting available so far does not establish what drove the earlier swings.

The CDC reported 2,289 confirmed cases in all of 2025. It says 96% of this year's cases were tied to outbreaks, and its counts are preliminary and subject to revision.

Pennsylvania has been a major center of transmission. The Associated Press reported on Oct. 30 more than 1,350 cases in the state, over a third of them in Lancaster County, while community leaders said infections were likely undercounted. State tallies do not themselves decide the outcome, since only the CDC's counter counts.

The CDC updates its counter weekly, using confirmed cases that jurisdictions notified it of as of noon Thursday. Future reports will show whether the total reaches 6,500. Reporting delays and revisions can change the count, and the agency assigns cases to years by the week of rash onset, which can differ from the calendar boundary.