Measles 'Eliminated' in US? Maybe Not for Much Longer

America's measles problem is back in the spotlight, and this time it could cost the country a public health milestone it's held for a quarter century. Over the past year, more than 2,200 people across 45 states have been sickened by measles—the highest tally in more than 20 years—with at least 150 mostly unvaccinated children hospitalized and three deaths, the first measles fatalities in a decade, per the New York Times. Texas has logged more than 800 cases, with South Carolina close to 445, and sizable outbreaks have hit Utah, Arizona, New Mexico, and Kansas, according to CDC data through mid-January. The virus is still circulating, with ongoing clusters along the Utah-Arizona border and in South Carolina.

"It is startling, because just a few years ago measles was very rare in the United States," Johns Hopkins epidemiologist Caitlin Rivers tells CNN. Now, an international panel will decide whether the US still qualifies as having "eliminated" measles, a status achieved in 2000 by not logging a continuous spread of the disease for at least a year, per the Times. To lose that designation, officials must show that the same chain of transmission has persisted for more than 12 months.

That's where things get tricky: Scientists need genetic sequences of the virus from different outbreaks, plus solid information on how it moved between communities. Many infections go unreported, and some patients are unwilling to share details about travel or their sickness, making it hard to tell whether, for example, Texas' 2025 outbreak is directly linked to those in Utah, Arizona, or South Carolina. The CDC is now racing to collect and analyze samples with state and local health departments before presenting its data to the Pan American Health Organization on April 13.

Canada lost its own measles elimination status last year after a prolonged outbreak, and some US experts say a similar ruling here would be a symbolic blow rather than a trigger for travel restrictions. Still, officials warn that regaining control could be much tougher this time. Vaccination rates would need to rise sharply, but public health leaders say deep political divisions over vaccines have made that goal far more difficult than when measles was declared eliminated 25 years ago. "Losing measles elimination status is an official acknowledgement that the country is on the wrong path," Brown University epidemiologist Jennifer Nuzzo tells Scientific American.