A case of measles has been confirmed in an Orange County resident, an unvaccinated toddler who by report has not traveled outside of the area or had known exposures. This case is not linked to the other measles case reported in a traveler due to the timing of illness. The OC Health Care Agency’s (HCA) Communicable Disease Control Division (CDCD) is reaching out to all identified contacts. No exposures in public locations have been identified.
Providers should increase their suspicion for measles in those with fever and rash illness and remember to report suspect cases to CDCD immediately at 714-834-8180.
Measles is an acute viral illness typically presenting with fever, cough, coryza, and conjunctivitis, followed 3-5 days later by a rash. The maculopapular rash typically begins on the face and spreads down the torso and out to the extremities. The incubation period for measles ranges from 7-21 days after exposure and individuals are infectious from 4 days prior to rash onset until 4 days after rash onset. Measles is highly contagious and spreads via airborne transmission.
Individuals can be presumed to be immune to measles if they were:
- born prior to 1957, OR
- have received two doses of measles containing vaccine, OR
- have documented positive IgG titer, OR
- documentation of prior disease.
Provider Recommendations and Resources
Management of Suspect Cases
Providers seeing a suspect case of measles should contact CDCD immediately at 714-834-8180 (staffed 24 hours per day).
Suspect cases of measles should be placed immediately in airborne isolation and evaluated wearing personal protective equipment including N-95 respirator, eye protection, gown and gloves.
Settings without respiratory isolation rooms should consider seeing the patient at the end of the day. If a suspect case is seen in a non-respiratory isolation room the room should be left empty for at least one hour.
Testing
The recommended test is detection of measles virus RNA by PCR of throat (preferred) or nasopharyngeal swab specimens. Urine specimens can also be collected and may be more sensitive latter in the illness.
It is strongly recommended that specimens for measles virus testing be submitted to Orange County Public Health Laboratory (OC PHL), as testing can be completed more quickly (usually within 24 hours) rather than sending to a commercial laboratory, speeding control activities. CDCD can arrange pick up of appropriate specimens for rapid test turnaround by contacting us at 714-834-8180. Specimens require HCA CDCD approval prior to submission.
Appropriate PCR specimen collection is performed by swabbing of the throat or nasopharynx using a swab made of synthetic material, such as nylon, polyester or Dacron (not cotton or with wood) placed in a screw capped container with viral transport media (VTM) or universal transport medial (UTM). Specimens should be maintained at 2-8◦C and transported within 72 hours.
Disease Investigation and Response
In the event that a confirmed measles case sought care at your facility, HCA will need the following information as soon as possible:
- Documented immunity status for all staff
- Time when the infectious case was present at the facility
- A list of all exposed patients and staff
This information is imperative to have in a timely manner in order to provide timely post exposure prophylaxis.
Post-exposure Prophylaxis
- Measles-Mumps-Rubella (MMR) and immune globulin (IG) is effective as post-exposure prophylaxis (PEP) when administered within the appropriate interval from exposure.
- Susceptible persons >6 months of age with 1 or no documented doses of MMR may receive MMR vaccine to decrease their risk of developing severe disease if not contraindicated.
- Children 6-11 months of age may receive either MMR vaccine within 72 hours of exposure or IG within 6 days of exposure to decrease their risk of severe disease.
- Individuals with a contraindication to MMR vaccine may receive IG < 6 days after date of last exposure to prevent disease. However, only IG administered < 6 days after first exposure to measles is considered adequate PEP for public health contact management. Persons who receive IG > 6 days after the first exposure to the case while the case is infectious should be placed in quarantine, avoiding contact with non-immune individuals for a period of 21 days from last exposure.
Isolation & Quarantine
Exposed individuals who do not have documented immunity to measles, had a known exposure to measles, and who have not received PEP (MMR vaccine <72 hours of first exposure) or (IG <6 days of first exposure) should quarantine, avoiding contact with non-immune individuals for a period of 21 days from last exposure.
Prevention
Unexposed but not immune individuals should be vaccinated unless there is a contraindication.
Travelers should make sure that they are up to date with measles vaccination prior to travel. Infants 6 months up to one-year of age, who are traveling internationally, are recommended to receive a dose of MMR vaccine prior to travel (Plan for Travel | Measles (Rubeola) | CDC).
Additional Resources
- HCA CDCD – Measles
- California Department of Public Health (CDPH) – Measles
- CDPH – Measles Healthcare Exposure Investigation Quicksheet
- Centers for Disease Control and Prevention – Measles
For questions or concerns, please contact the Communicable Disease Control Division at 714-834-8180.
Recent Measles Trends in California
- Case Surge: In 2025, California recorded 25 confirmed cases, an increase from 15 cases in 2024 and only 4 cases in 2023.
- 2026 Activity: As of late January 2026, California has already confirmed multiple cases, including the Orange County toddler with no travel history and cases in Los Angeles and Shasta counties.
- Domestic vs. Travel: While most historical outbreaks were linked to international travel (like 5 out of 6 outbreaks in 2019), cases with unknown sources or domestic exposure are becoming more frequent as U.S. case counts reached a 30-year high in 2025.
Local & Statewide Context
- Orange County Specifics: In 2025, Orange County reported only 1 case. The current case in the unvaccinated toddler is notable because it is the second confirmed case in the region for 2026 and lacks a clear travel link.
- Vulnerability: Health officials note that 16 California counties have fallen below the 95% herd immunity threshold for the MMR vaccine, increasing the risk of community transmission.
- National Context: The U.S. recorded over 2,200 cases in 2025, the highest in decades, which facilitates the “no-travel” domestic spread seen in this recent OC case.
You can track the most recent local updates through the OC Health Care Agency (HCA) Pressroom or view statewide data on the California Department of Public Health (CDPH) Measles page.