U.S. measles cases hit 1,277—the worst outbreak since the disease was declared eliminated in 2000, surpassing 2019's peak.

The Pan American Health Organization says the most affected age groups are children under the age of 5 and adolescents aged 10 to 19. Gaps in routine immunization are helping to fuel outbreaks of a disease that was considered eliminated in America in 2000, when less than 100 cases were reported, the organization says.

For the past 25 years, measles has been considered eliminated in the U.S. because it has not continuously spread over a yearlong period. There are still periodic outbreaks, howeve