SACRAMENTO (CBS News) -- California Gov. Jerry Brown declared a state of emergency Friday due to a lack of vaccines in a deadly hepatitis A outbreak in several California counties, CBS Los Angeles reports.

The declaration allows the state to "increase its supply of hepatitis A vaccines in order to control the current outbreak," Gov. Brown said in a statement.

While immunizations from the federal vaccine program have been distributed to at-risk populations in affected areas in Los Angeles, San Diego and Santa Cruz counties, Brown's proclamation allows the California Department of Public Health (CDPH) to immediately purchase and distribute vaccines to affected communities.

California is experiencing the largest hepatitis A outbreak in the United States transmitted from person to person -- instead of by contaminated food -- since the vaccine became available in 1996.

There are 576 cases reported throughout California, the vast majority in San Diego.

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, the county director of public health said in a news conference.

Anyone working with individuals at high risk of contracting the disease -- including health care providers, food-service workers and shelter employees -- were urged to get vaccinated.

San Diego County officials earlier this month declared a public health emergency because of the liver disease outbreak that has killed 16 people and hospitalized 300 more since November. Their homeless population has been hit the hardest.

In Santa Cruz County, at least 69 people have been diagnosed with hepatitis A amid a smaller outbreak that broke out in April, according to the San Diego Union Tribune.

"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," said Dr. Sharon Balter, the chief of the department's communicable disease control program.

The county typically sees about 40 to 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.