A Hepatitis A outbreak is on the rise in Hawaii. The state Health Department revealed at least 135 people have been affected by the virus — all adults — and 39 people have required hospitalization, Hawaii News Now reported.

Health officials said the outbreak is mostly affecting people residing on Oahu. However, seven of the people who have contracted the virus live on neighboring islands and one visitor is from the mainland.

The current Hepatitis A outbreak — onset between June 12 and July 24 — is the largest in the state’s history.

According to the Centers for Disease Control and Prevention, the last major outbreak of Hepatitis A in the U.S. was in 2013 and caused by frozen pomegranate seeds from Turkey. 162 cases of the virus were linked to that specific outbreak. Eight cases were reported in Hawaii.

It’s unclear what sparked the latest outbreak in Hawaii. However, many of the people who have gotten sick from the virus are food service workers, including a Chili’s Kapolei employee and workers at Baskin-Robbins, Costco Bakery, Sushi Shiono and Taco Bell.

A Hawaiian Airlines Flight attendant has also been reported infected with Hepatitis A.

As per Food Safety News, neither Chili’s nor Hawaiian Airlines are being considered sources of the outbreak. Hawaiian Airlines was named because the infected attendant served inflight food and drinks to traveling passengers.

Customers who may have visited any of the food establishments listed have been encouraged to contact their health provider, as the virus can infect people for a month or longer before showing any symptoms of illness.

Those who have not been exposed to the virus are also being encouraged to get vaccinated. However, basic hygiene practices such as hand-washing and thoroughly cooking food can prevent the spread of the virus.

Read on for a few facts on how Hepatitis A spreads and how it can be prevented below:

1. Hepatitis A is a virus primarily spread when an uninfected and unvaccinated person ingests food or water that is contaminated with fecal matter from an infected person.

2. Although the virus doesn’t lead to chronic liver disease like Hepatitis B and C, it can lead to liver disease and cause acute liver failure.

3. Symptoms of Hepatitis A include fever, malaise, loss of appetite, diarrhea, nausea, abdominal pain, dark-colored urine and jaundice. All the symptoms can range from mild to severe, but not everyone infected with the virus may suffer from Hepatitis A indicators.

4. Adults are more likely to experience symptoms of Hepatitis A than children, and most severe diseases and fatalities linked to the virus are higher in older age groups.

5. Recovering from symptoms can take weeks or months as there is no specific treatment for Hepatitis A.

6. Hepatitis A is best prevented by improved sanitation, food safety and immunization. There are injectable vaccines available in the US. There is also a live oral vaccine available in China.