An unvaccinated visitor who later tested positive for measles may have exposed emergency patients at Sharp Memorial Hospital in San Diego on March 11, the county’s public health department warned Wednesday.

The notice, published just after 4:30 p.m., identifies the potential window of exposure as running from 11:22 a.m. to 4:35 p.m. and anyone who was cared for or who accompanied someone who was cared for during this five-hour span is asked to call the county health department at 619-692-8499.

According to the county’s statement, the patient was an “out of state adult” who was evaluated for fever but who had no measles symptoms at the time of their visit.

While it is standard operating procedure for the county’s public health department to identify and interview everyone who was known to have visited a location where the highly contagious virus was detected, health care records generally do not capture everyone who visited a given location at a given time.

California and the nation as a whole has recently experienced a growing measles outbreak, with 29 cases reported in California and more than 1,300 nationwide. However, San Diego County has thus far not recorded its first case in 2026. Last year, one local case was reported, though it was linked to international travel.

The case at Sharp Memorial is not considered a local case as the patient does not reside in San Diego County.

Dr. Sayone Thihalolipavan, the county’s public health officer, stressed the importance of identifying cases quickly, given how easily the virus spreads.

“Measles is extremely contagious and can be spread easily by coughing, sneezing or simply sharing the same air space as an infected person,” Thihalolipavan said in the county’s statement.

It takes between seven to 21 days after exposure for measles symptoms to develop. They can include fever, cough, runny nose and red eyes. A distinctive red rash usually appears between one and four days after initial symptoms, spreading from the face to the rest of the body. People are considered contagious four days before and four days after the rash appears.

Some, including infants younger than 12 months, people who have not been vaccinated and those with weakened immune systems are at the greatest risk of severe illness.

“There is no treatment for measles and vaccination is the best protection,” said Thihalolipavan. “We continue to see declining measles vaccination rates regionally, which is a concerning trend.”

Measles complications can include: diarrhea, ear infections, pneumonia and, rarely, encephalitis or death. Bed rest, fluids and fever control are the main treatments.