Measles Activity in California

Data were extracted on measles cases with an estimated rash onset or episode date from January 1, 2026 through the last week indicated, from California Confidential Morbidity Reports and/or Laboratory Reports that were submitted to CDPH and which met the surveillance case definition for that disease. If the rash onset was unknown, the earliest available date from the following was used as episode date: symptom onset, diagnosis, laboratory specimen collection, reported to public health. Because of inherent delays in case reporting and depending on the length of follow-up of clinical, laboratory and epidemiologic investigation, cases with eligible onset dates may be added or rescinded after the date of this report.