The Hawaii Department of Health is conducting an investigation into at least 12 adults on Oahu infected with hepatitis A.

The reported illnesses began June 16-27, and six adults were hospitalized, according to a department press release.

Symptoms include fever, nausea, loss of appetite, abdominal pain and jaundice, according to the U.S. Centers for Disease Control. Hepatitis A is typically spread via contaminated food or water, but can also spread via household members or sexual partners, the CDC says.

The Health Department encourages people with symptoms to immediately see a doctor. Everyone else should wash their hands frequently and consider getting vaccinated. Here is a list of Hawaii’s vaccinating pharmacies.

Health Department Director Virginia Pressler said in the release that while most children and adults have been vaccinated, those who have not are vulnerable.