How big is Pennsylvania’s measles outbreak?

News of a fifth measles death in Pennsylvania underscores a longstanding problem with the disease: the full scope of the outbreak, both in the state and nationally, is not known or even knowable, because only confirmed cases get reported. As of Wednesday, that confirmed total stood at 943 in Pennsylvania, roughly a quarter of the 2026 national total.

Confirmed cases capture only part of the picture. About 20% of infected people end up needing hospital care and another portion will see a doctor, but some will never come to the attention of public health authorities at all. That is especially true in Pennsylvania, where a number of counties have large Amish populations — and it was true in last year's outbreak in Mennonite colonies in Texas. People in these communities do not interact much with the wider world, measles vaccination rates are low, families are large, and individuals may not seek care unless the illness becomes severe.

At some point researchers will produce modeling estimates that may give a better idea of how large the outbreak actually is, but for now only a portion of the iceberg is visible. "It is much worse than is being claimed," said Paul Offit, director of the Vaccine Education Center at the Children's Hospital of Philadelphia. "I think we don't know how bad."

The same STAT newsletter also covered a new analysis of NIH funding: the agency awarded $34 billion to universities in fiscal year 2026 across 58,000 projects, compared with a historical average of 63,700 before the second Trump administration, with further reductions in awards tied to health disparities, race, and ethnicity; a survey of about 50 NIH-funded researchers found grant review delays are slowing their work. A separate First Opinion argued that collecting data from medical tents on race courses is the best way to help marathon organizers prepare for heat stroke as a growing climate-related risk.