A measles outbreak in the Sacramento region, the third and largest in California so far this year, has brought the state’s year-to-date measles cases to 39 — far surpassing yearly totals for the last several years.
The ongoing outbreak in Sacramento and Placer counties, which began in late February and has grown to 17 cases — including four new cases over the past week — will likely continue another 21 days, the incubation period for measles, state health officials said Tuesday.
“With measles, this has been a significant year for us in that we are only a quarter of the way through the year and we already have 39 cases,” Dr. Eric Sergienko, chief of the California Department of Public Health’s communicable disease control division, said in a briefing with medical professionals.
California reported 25 measles cases in 2025, 15 in 2024, four in 2023, none in 2022 and 2021, and four in 2020, according to state data.
Of the 39 cases so far this year, 85% have been in people under age 20, and 95% have been in people who were unvaccinated or whose vaccination status was unknown. People whose status is unknown are most likely unvaccinated.
The rise in measles in California coincides with a national resurgence of the vaccine-preventable disease. The United States in 2025 reported the highest number of measles cases in 30 years, mostly driven by large outbreaks in Texas and South Carolina. The U.S. declared measles eliminated in 2000, but is now at risk of losing that status.
A measles outbreak is defined as three or more related cases. The two previous outbreaks in California this year were in Riverside County, where three cases were within one family, and Shasta County, where nine cases were within a church group, Sergienko said.
Prior to these two outbreaks, California had not had a measles outbreak since early 2020, with four cases. The last major outbreak was in 2019, when the state reported 73 cases, including 21 associated with an outbreak in a health care setting.
The first case in the Sacramento and Placer outbreak was reported in an unvaccinated toddler who had recently traveled to South Carolina, which is in the midst of the largest measles outbreak in recent history, with nearly 1,000 cases.
The two other outbreaks, in Riverside and Shasta counties, were also likely linked to residents who traveled to parts of the country that were experiencing measles outbreaks, Sergienko said.