There were 97 reported cases of measles in the first quarter of the year, the Centers for Disease Control and Prevention (CDC) reports, representing nearly a third of all cases since the beginning of 2020.

“Risk for widespread U.S. measles transmission remains low because of high population immunity,” the CDC wrote in a report released last week. “However, because of the increase in cases during the first quarter of 2024, additional activities are needed to increase U.S. routine measles, mumps, and rubella vaccination coverage, especially among close-knit and undervaccinated communities.”

The CDC began analyzing reported measles cases after two outbreaks in 2019 in unvaccinated communities in New York. Its report noted 338 confirmed cases from Jan. 2020 to March 28, 2024. The jump in cases in the first quarter of this year represented a seventeenfold increase of the mean during the first quarter of the previous three years. CDC has reported an additional 24 cases since the end of March, bringing the year’s total to 121 as of April 11.

The CDC notes that 93 cases from the first quarter were directly imported from other countries, either from foreign visitors (34) or U.S. residents (59), almost all of whom were either unvaccinated or whose vaccination status is unknown. The increase in measles cases globally and the decline in vaccination rates in this country make for a risky mix.

“Increasing global measles incidence and decreasing vaccination coverage will increase the risk for importations into U.S. communities, as has been observed during the first quarter of 2024,” according to the report, “further supporting CDC’s recommendation for persons to receive MMR vaccine before international travel.”