Hawaii's Department of Health is investigating an outbreak of hepatitis A on Oahu.
The department said Friday there are at least 12 cases of hepatitis A infection in adults. Six of them have required hospitalization.
Onsets of the illnesses range from June 16 through June 27.
Health officials say the virus can be spread by eating contaminated food, drinking contaminated water, close personal contact or sex. Symptoms include fever, fatigue, appetite loss, abdominal discomfort and diarrhea.
Health Director Dr. Virginia Pressler says it's a vaccine-preventable disease. She says that while it's a routine childhood vaccination, many adults haven't been vaccinated and remain susceptible.
The vaccine is readily available at local pharmacies.
Frequent handwashing can also help prevent spreading hepatitis A.