The Massachusetts Department of Public Health announced Monday that there is an outbreak of hepatitis A in the state. So far, all cases have been among people or are homeless and, or have substance use disorder.

The MDPH issued a public health alert saying that since April of this year, 65 cases of acute hepatitis A have been reported — nearly half of those in Boston. The MDPH is encouraging local health officials to work with community-based organizations that provide services to people experiencing homelessness or using drugs to get people vaccinated and educated about the disease.

Dr. Catherine Brown, the state epidemiologist, says people often get the different types of hepatitis confused.

“Hepatitis all by itself really just means inflammation of the liver,” Dr. Brown says. “When we talk about hepatitis, we’re often referring to hepatitis caused by a virus, and then there are different kinds.”

Hepatitis A is spread in contaminated environments, or from person to person, whereas B is transmitted by very close direct contact. Hepatitis C is a blood borne virus. There are vaccines for hepatitis A and B, but not hepatitis C.

Dr. Brown says the general public shouldn’t be too concerned since this outbreak is currently in a discrete population, but getting vaccinated and washing hands frequently are both always a good idea.

The hepatitis A virus can cause a range of symptoms, from relatively mild to very serious.

“We’re seeing about a 94 percent hospitalization rate in this population,” Dr. Brown says. She says the population affected by this outbreak has a high rate of previous hepatitis C, which means the new virus is much more severe than usual. There’s no specific treatment for hepatitis A, but Dr. Brown is encouraging anyone who thinks they might have the virus to seek medical help right away. That will also hopefully limit the spread of the disease.

Symptoms can include fever, tiredness, loss of appetite, stomach pain, nausea, diarrhea, and jaundice. According to the MDPH, “Teens and adults are more likely to have these typical symptoms than children. Young children with hepatitis A often have mild or no symptoms at all. Symptoms usually last less than two months. Some adults can feel sick for as long as six months, but this is rare.”

On Wednesday the Massachusetts DPH will be talking to local boards of health about how to help identify at risk populations in their communities, and then how to reach them for education and vaccination.