This is an archived article and the information in the article may be outdated. Please look at the time stamp on the story to see when it was last updated.

Officials alerted residents on Tuesday of possible measles exposure sites after confirming the first case of measles among Orange County residents this year.

The measles patient, a Placentia resident in her 20s, was diagnosed after a recent trip abroad to a country “experiencing widespread measles activity,” the O.C. Health Care Agency said in a news release.

The woman has been contagious since April 23 and is at risk of spreading the illness to others until Wednesday, May 1, officials said.

The patient is now under voluntary isolation inside her home, authorities said.

However, she previously visited the following locations while infectious, potentially exposing others to the virus since it spreads easily by air:

• The business park at 5 Hutton Centre Drive in Santa Ana daily from April 23 to 25, between 7:45 a.m. and 7:15 p.m.

• St. Jude Emergency Department at 101 E. Valencia Mesa Drive in Fullerton on April 27, from 7 a.m. to 9 a.m.

• AMC Movie Theater at 1001 S. Lemon St. in Fullerton beginning April 25 at 11 p.m. to April 26 at 4 a.m.

Anyone who visited those spots around those time periods should review their vaccination history and monitor themselves for symptoms, which include fever, cough, a runny nose and red eyes. A rash usually appears 7 to 21 days after exposure, according to public health officials.

If you have not developed any symptoms 21 days after the possible exposure, you are no longer considered at risk of developing measles.

People who haven’t been vaccinated and those with weakened immune systems are at the highest risk. Roughly 90 percent of unvaccinated people fall ill 7 to 21 days after exposure, authorities said.

The U.S. is currently experiencing the highest number of measles cases since 1994, with more than 700 cases confirmed across the nation as of Monday, according to the Centers for Disease Control and Prevention.

That includes 38 cases in California. In Los Angeles County, officials have declared a measles outbreak with six residents confirmed to have contracted the illness this year.

Anyone who is not vaccinated against the highly contagious illness should speak with their health care provider. People with measles can spread the virus before they know they are infected and up to four days before a rash begins to develop.

For more information about the infection and immunization guidelines, visit the O.C. Health Care Agency or CDC website.

33.861903 -117.920152