Health officials said Tuesday that Los Angeles County has a hepatitis A outbreak based on two "community-acquired" cases that cannot be traced back to San Diego County or Santa Cruz.

"We are in the situation of a hepatitis A outbreak ... as of this morning," Public Health Department Director Barbara Ferrer told the Board of Supervisors.

Most cases to date have been identified in patients who are homeless or drug users, but include workers at a health care facility working with those patients, Ferrer said. Ferrer urged anyone working with individuals at high risk of contracting the disease -- including health care providers, food-service workers and shelter employees -- to get vaccinated.

"The safest thing you can do if you work with a high-risk population or if you are worried ... is to get vaccinated," she said.

Children have been routinely vaccinated since 1999. But many adults lack protection against the virus.

"It is a good idea for everyone to talk to their doctor," said Dr. Sharon Balter, the chief of the department's communicable disease control program.

But Balter said the county should focus on the homeless population, where the greatest risk lies. Ferrer agreed.

"The reason we're particularly concerned (now) is because we have an outbreak in San Diego and we have an outbreak in Santa Cruz," and the contagion is in a "population not easily contained," she said.

The county typically sees about 40-60 cases of hepatitis A annually from the population at large, with a concentration often found among food-service workers. But those patients can be readily tracked and follow-up can be scheduled by phone or email, something that's not possible when patients are living on the street.

Hepatitis A is a highly contagious liver disease. Some individuals with hepatitis A may not have any symptoms, while others other may suffer mild symptoms over a period of weeks that can be treated with rest, good nutrition and fluids.

"Most people recover completely and don't have lasting liver damage," Ferrer said. However, both those who have other health issues or weakened immune systems can be hospitalized and suffer permanent liver damage.

And even those without symptoms can spread the disease, which mostly occurs though contact with feces via surfaces or sexual contact. Keeping hands clean can prevent contagion and part of the county outreach to homeless individuals will include distributing hand sanitizer.

An aggressive vaccination campaign is underway.