since 2000. As the virus takes hold in U.S. communities with low vaccination rates, health experts fear that spread could stretch on for a year. Two unvaccinated elementary school-aged children died from measles-related illnesses in the epicenter in West Texas, and an adult in New Mexico who was not vaccinated died of a measles-related illness.

North America has two other ongoing outbreaks. One in Ontario, Canada, has resulted in 1,243 cases from mid-October through Tuesday. And the Mexican state of Chihuahua had 844 measles cases and one death as of Friday, according to data from the state health ministry. Health officials in Mexico and the U.S. say all three outbreaks are of the same measles strain.