San Diego County public health officials issued an urgent exposure alert this week after a confirmed measles case was traced to the Sharp Memorial Hospital Emergency Department at 7901 Frost St. in San Diego on March 11.

An unvaccinated traveler from out of state who was infectious at the time visited the ER between 11:22 a.m. and 4:35 p.m. that day. The individual did not display the characteristic rash typically associated with measles, potentially leaving dozens of patients and staff unknowingly exposed.

Anyone who was in the emergency department during that window is urged to call (866) 358-2966 immediately to determine their immune status and risk level.

The exposure comes amid a broader surge in measles activity. As of March 16, California has confirmed 29 measles cases this year. Nationally, the Centers for Disease Control and Prevention has confirmed 1,362 cases as of March 12 — a stark contrast to the single San Diego County case recorded in all of 2025.

Measles is one of the most contagious pathogens in existence, capable of remaining suspended in the air for up to two hours after an infected person has left a room. Infected individuals are contagious for four days before the characteristic red rash appears, often displaying only cold- or flu-like symptoms during that period.

"There is no treatment for measles and vaccination is the best protection," said Dr. Sayone Thihalolipavan, County Public Health Officer. "We continue to see declining measles vaccination rates regionally, which is a concerning trend."

Infants under 12 months, pregnant individuals, and those with compromised immune systems face the highest risk of severe complications, including pneumonia and encephalitis. The MMR vaccine is 97% effective after two doses. Those unsure of their vaccination status or who develop a fever and cough should contact their healthcare provider by phone before arriving at any clinic or emergency room.