Health officials in Contra Costa County have confirmed a measles infection in a person who was mingling in public places for about a week before being discovered.

Contra Costa Health is notifying the public about the infection and said people may have been exposed at several locations in Walnut Creek and Lafayette between Dec. 17 and Dec. 24.

The infected person was at the Anthropologie store on South Main Street in Walnut Creek on Dec. 17 or Dec. 19, at the Macy’s and ALO stores at Broadway Plaza in Walnut Creek and the Apple Store on South Main Street in Walnut Creek on Dec. 18.

They were also at STAT Med on Mount Diablo Boulevard in Lafayette on Dec. 21 and the Kaiser Permanente Walnut Creek Emergency Department on South Main Street on Dec. 23 and Dec. 24.

“People who were at these locations during the dates listed above may be at risk of developing measles, especially if unvaccinated, pregnant or immunocompromised,” county health officials said in a news release Monday. “Measles can develop seven to 21 days after exposure. If you were at these locations during these times, you should confirm with your healthcare provider that you have been fully vaccinated against measles or have had measles infection in the past.”

Measles is a highly contagious respiratory virus that can linger in the air or on surfaces for over an hour after a contagious person leaves the area, according to health officials.

Also, someone can spread the virus even before they develop symptoms, which include fever, cough, runny nose, red eyes and a rash.

People who have not done so already are encouraged to get two doses of the measles-mumps-rubella, or MMR, vaccine.

“A large majority” or county residents have been given the MMR vaccine, which lasts a lifetime and greatly reduces one’s vulnerability to the disease, county officials said.

As of Dec. 23, 2,012 confirmed measles cases were reported in the United States, according to the Centers for Disease Control and Prevention, with 24 of those being in California.

More information about measles can be found on the Contra Costa Health website and from the CDC.

Kiley Russell writes primarily for Local News Matters on issues related to equity and the environment. A Bay Area native, he has lived most of his life in Oakland. He studied journalism at San Francisco State University, worked for the Associated Press and the former Contra Costa Times, among other outlets. He has covered everything from state legislatures, local governments, federal and state courts, crime, growth and development, political campaigns of various stripes, wildfires and the aftermath of Hurricane Katrina.