The Centers for Disease Control and Prevention said that 125 measles cases have been reported across 17 states this year.
More cases of measles have been reported in 2024 so far than in all of 2022.
Illinois has seen the largest number of cases after an outbreak at a Chicago migrant shelter.
While cases in the shelter have declined, the city warned that more cases have been reported with no connection to the shelter. They say doctors should consider giving an "accelerated" second dose of the measles vaccine to young children.
The CDC attributed the spread to unvaccinated international travelers coming to the U.S., despite the fact that the U.S. officially eliminated local spread of the virus in 2000.
The CDC's disease forecasters estimate that by the end of the year, the U.S. will reach 300 measles cases.
"It's important to remember that the overall measles outbreak risk to the general population is low; however, measles cases are increasing globally, increasing the chance of importations into the U.S. and subsequent risk of outbreaks, particularly in communities with low vaccination rates," the agency's forecasters wrote.
