Yolo County Health and Human Services Agency’s Public Health Branch has confirmed that a resident of West Sacramento has been diagnosed with measles. This is the 13th confirmed case of measles in California in this year. Prior to two cases reported in 2024 among Yolo County residents who traveled internationally, the county had not seen a measles case since 2015.

The affected adult, whose vaccination status is unknown, is experiencing mild illness and is recovering at home. The source of the infection is under investigation. The individual may have been exposed during recent air travel to a state without a known outbreak or may have contracted the virus locally.

While no additional local cases have been identified, measles has recently been detected in wastewater samples collected at the Sacramento Regional Wastewater Treatment Plant from May 20-24 and again from June 2-3. Only a small portion of the wastewater processed at the plant originates from West Sacramento. Although the June detections may be linked to this individual, the May wastewater detections cannot be. An investigation into the source of the earlier detections is ongoing and it remains possible that another unknown individual with measles was present in the area.

Measles is extremely contagious, spreading through the air and via contaminated surfaces. Contact tracing conducted by Yolo County Public Health indicates that the individual visited a healthcare facility while infectious and may have exposed patients, visitors, and healthcare providers at the following location:

Sutter Davis Hospital, Emergency Department at 2000 Sutter Place in Davis.

May 31-June 1, between 10:12 p.m. and 1:42 a.m.

June 2, between 2:42 p.m. and 1:23 a.m.

Sutter Davis Hospital has identified patients and staff who may have been exposed and is collaborating with local health departments to notify those individuals. The hospital took all the necessary safety precautions once measles was suspected and notified Yolo County Public Health.

However, visitors present during those times may not yet have been identified. Anyone who was at the above location during the dates and times listed may be at risk of developing measles and is advised to contact Yolo County Public Health’s Communicable Disease Program at (530) 666-8670 (leave a message and a team member will return your call). A specialized team is available to determine whether residents are at risk and whether preventive measures, such as MMR vaccine, are recommended. The general public, aside from those who were at the facility during the dates and times listed, is not at risk of developing measles from this individual.

“This case of measles in our community is a good reminder that while international travelers and those traveling to outbreak areas within the U.S. are at highest risk of measles, residents can also encounter measles during travel to non-outbreak areas or even within our local community. It is important to check your measles vaccination status to make sure you are protected against measles infection,” stated Yolo County Public Health Officer Dr. Aimee Sisson.

Measles can be safely prevented with a measles, mumps, and rubella vaccine (MMR) or a measles, mumps, rubella, and varicella vaccine (MMRV). They are administered in two doses (typically given at one year and four to six years old) and are highly effective. Two doses are 97% effective in preventing measles, and one dose is 93% effective.

Globally, vaccinations against measles fell during the COVID-19 pandemic, and cases of measles have surged in many countries. There have been over 1000 cases of measles in the United States in 2025, compared to 285 cases in all of 2024. These cases include individuals who were infected during international travel and individuals infected within the United States. Most cases this year are linked to domestic transmission, particularly in Texas, New Mexico, and Oklahoma. Nationwide, 96% of measles have occurred in individuals who were unvaccinated or whose vaccination status was unknown. Of the 12 prior cases reported in California this year, 10 were linked to international travel.

Yolo County Public Health encourages all residents to verify their measles vaccination status. Adults who have not had measles in the past (those born in the U.S. before 1957 are presumed immune) and do not have at least one MMR vaccination should contact their healthcare provider to get vaccinated. Some adults, including those planning travel, may need a second dose of MMR. Measles vaccine doses administered between 1963 and 1967 may need to be repeated. Children who are not up-to-date should also visit their healthcare provider. Children as young as six months may receive an early dose before travel, and those between one and four years old may receive their second dose early in preparation for travel.

Individuals typically develop symptoms eight to 12 days after exposure to measles. Measles symptoms begin with a fever, cough, red and watery eyes, and a runny nose, followed by a rash three to five days later that starts on the head and spreads downwards. Measles can result in serious complications and even death for young children and vulnerable adults. Exposed people with symptoms should stay home and away from others and contact Public Health immediately. Persons needing care for their measles symptoms should call their healthcare provider’s office in advance, rather than visit an office directly, so that the facility can take measures to prevent exposure to others.

Nearly all health insurance plans are required to cover the cost of MMR and MMRV vaccines. Insured persons should check with their healthcare provider or a local pharmacy to see what vaccines are offered. Uninsured or underinsured children and adults can access free or low-cost vaccines at clinics enrolled in the Vaccines for Children (VFC) and Vaccines for Adults (VFA) programs. For a list of clinics that offer free or low-cost immunizations for individuals who are uninsured or underinsured, call 2-1-1 or visitwww.YoloCounty.gov/ImmunizationClinics. For more information on measles, visit www.CDC.gov/Measles or www.cdph.ca.gov/Programs/CID/DCDC/Pages/Immunization/measles.aspx.