More cases of measles were reported Friday as public health officials issued an alert to caregivers confirming that an outbreak is occurring in Los Angeles County.

Health officials said a day before they were looking into seven cases of the measles, but by Friday that figure had grown to nine.

The alert was directed toward caregivers in hospitals and other medical centers and clinics.

“Health care providers should consider the diagnosis of measles among persons presenting with a febrile rash illness,” according to officials with the Los Angeles County Department of Public Health. “Immediately institute respiratory and airborne precautions for all persons with a measles like rash and fever.”

It was unclear where the outbreak began. Health officials said a location would be given when they find it necessary, according to a release Thursday.

“Measles is a highly contagious viral disease that spreads from person to person through coughing or sneezing,” said Dr. Jeffrey Gunzenhauser, interim health officer for Los Angeles County in a statement. “To protect individual health and to prevent the spread of measles to others, we urge residents who are not immunized to get the measles-mumps-rubella (MMR) vaccine as soon as possible. Two doses of MMR vaccine is highly effective in preventing measles and is the best way to protect against disease.”

California experienced its worst measles outbreak in 15 years beginning in December 2014, when a person infected with the measles visited Disneyland. California experienced its worst measles outbreak in 15 years in December that stemmed from an infection at Disneyland. The disease affected more than 130 California residents and dozens more nationwide.

The event also cast a spotlight on immunization rates among schoolchildren, and some districts told unvaccinated children to stay home. As a result of the outbreak and climbing whooping cough rates, one of the nation’s toughest childhood vaccination bills was signed into law in June 2015 by Gov. Jerry Brown, who wasted no time approving legislation that for months has evoked passionate debates and protests across the Golden State.

Measles symptoms include fever that can last for days, followed by a cough, runny nose and a rash that first appears on the face and behind the ears and then affects the rest of the body. Death can occur from severe complications, experts said.