She is also the first confirmed case of measles to hit Orange County this year.
California health officials say a woman unknowingly infected with the measles went to the movies on the night of April 25. After realizing she was sick, she voluntarily isolated herself at her Placentia, CA, home.
Following reports in Los Angeles, Butte, and Sacramento, Orange County is the latest victim of the rapidly spreading disease.
The patient-a 20-something woman from Placentia-allegedly contracted the illness during worldwide travel "to one of many countries now experiencing widespread" activity, according to the OC Health Care Agency (HCA). They did not say whether she had been vaccinated against measles.
Measles is highly contagious, as it is airborne and can spread when an infected person coughs or sneezes.
The warning comes amid several major measles outbreaks nationwide and the highest number of measles cases across the nation in more than two decades.
Most people recover, but measles can lead to pneumonia, brain swelling and even death in some cases.
Hacker said local officials are in constant contact with the Centers for Disease Control and Prevention. According to the CDC, one dose of the MMR vaccine, which protects against measles, mumps, and rubella, is 93 percent effective at preventing measles, and two doses are about 97 percent effective. The CDC is also recommending infants 6 through 11 months receive one dose of the vaccine before global travel.
Anyone who does not know their vaccine status should speak to their health care provider.