California Gov. Jerry Brown has just issued an emergency declaration after an outbreak of hepatitis A that has killed more than a dozen people and has sickened hundreds of others. The outbreak began in southern California, in San Diego, Santa Cruz, and Los Angeles counties, especially in San Diego County where 490 people have become ill and 18 have died from the liver disease since this spirng.

A total of 13 people have also become ill in Los Angeles County, and the disease threatens to spread further in the state. It is the worst outbreak of hepatitis A in terms of person-to-person transition since a hepatitis vaccine was made available in the mid-1990s. The homeless appear to be suffering the most, and it appears to be spread due to poor sanitation and a lack of hand washing, or from using drugs.

Because of the declaration, state health officials will be able to start purchasing vaccines directly from manufacturers and hand them out at homeless communities where the disease has been most prevalent. Hepatitis A is a liver disease that results in nausea, abdominal pain, bowel problems, joint pain, jaundice, and other symptoms. It can cause liver failure and death in serious cases.

“Governor Edmund G. Brown Jr. today issued an emergency proclamation that allows the state to increase its supply of hepatitis A vaccines in order to control the current outbreak,” the statement from the governor reads. “Immunizations from the federal vaccine program have been distributed to at-risk populations in affected areas, but additional supplies are needed. Today’s proclamation gives the California Department of Public Health (CDPH) authority to immediately purchase vaccines directly from manufacturers and distribute them to impacted communities. Later today, CDPH officials will host a call for reporters regarding the current hepatitis A outbreak and efforts to increase the supply of adult hepatitis A vaccines.”