Massachusetts health officials are warning that a hepatitis A outbreak has hit the state, and it resembles a similar outbreak that occurred several years ago.
Ten cases have been confirmed since Sept. 1 of this year, with more than half occurring since Nov. 1, the Massachusetts Department of Public Health (MDPH) told ABC News on Tuesday.
Some of the cases have been severe, with seven requiring hospitalization, the department said. However, no deaths have been reported.
MORE: Nearly 450 patients at Massachusetts hospital may have been exposed to HIV, hepatitisThe patients are between ages 35 and 60 with a median age of 46, the MDPH said. Seven of the patients are men and three are women; eight patients are white and two are Hispanic, according to the MDPH.
Several of the patients reported being recently homeless or having unstable housing, as well as a history of injection or other drug use, according to an alert issued Monday by the MDPH. The department also said many of these patients had sought services at Boston-area clinics, shelters and substance use treatment facilities.
The patients do not have a history of travel outside of Massachusetts and do not share any common sources of food, drink or drugs, the MDPH said.
The MDPH said the cluster of cases is similar to a hepatitis outbreak that began in Massachusetts in April 2018 and ended in May 2020, which resulted in 563 cases and nine deaths. That outbreak mostly affected people experiencing homelessness or unstable housing and/or substance use disorder, the department said.
"There are similarities in risk factors between the cases reported here and those reported during the 2018-2020 outbreak of hepatitis A in Massachusetts," a spokesperson for the MDPH told ABC News. "Cases here report recent homelessness and/or drug use, including injection drug use. People who have unstable housing or are experiencing homelessness are at increased risk of hepatitis A infection."
During that period, there were also large clusters of hepatitis A in California, Indiana, Kentucky, Michigan, Tennessee, Utah and West Virginia, according to the department.
Hepatitis A is a very contagious liver infection caused by the hepatitis A virus, according to the Centers for Disease Control and Prevention.
The virus is found in the stool and blood of infected people and is spread through close, personal contact with an infected patient or by eating contaminated food and drink, even in microscopic amounts, the CDC says.
"This is one that, unlike the other hepatitis viruses that we are familiar with, this is one that is transmitted through the fecal-oral route," Dr. Shira Doron, chief infection control officer for Tufts Medicine, told ABC News. "So, it's not transmitted through blood and other body fluids like hepatitis C, for example."
"It's often a result of situations where they may be poor sanitation, overcrowding, poor bathroom facilities, things like that," she continued. "It's not entirely surprising that we're seeing another outbreak in a similar way to the last time we had this in Massachusetts, and it's affecting people who are homeless or have unstable housing because they experience risk factors of the virus."
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"You can have a change in the color of your stool where it becomes grey or loses color. That's a pretty distinct sign that should send you right to the doctor," Doron said.
The CDC says a person can transmit hepatitis A without showing symptoms and can do so up to two weeks before symptoms appear.
There are no specific treatments for hepatitis A, with doctors typically recommending rest, adequate nutrition and fluids, according to the CDC.
In rare cases, hepatitis A can lead to liver failure and death, but this is more common in those with underlying conditions such as chronic liver disease, the federal health agency said.
If someone has been exposed, there's a hepatitis A vaccine that can help prevent the virus from taking hold with a single shot given within two weeks of exposure.
There are also two types of hepatitis A vaccines that can be given as a preventative measure: One given as two shots six months apart, and the other being a combination vaccine that protects against hepatitis A and B and is given as three shots over six months.
MORE: Concerning clusters of severe hepatitis cases in children being investigatedDoron said vaccination is key to helping prevent the spread of hepatitis A. Currently, the CDC recommends children receive the vaccine at 1 year old and through age 18 if not previously vaccinated.
Additionally, the CDC recommends that high-risk adult groups -- including international travelers, men who have sexual contact with other men, people who use injection or non-injection drugs, people experiencing homelessness, people with chronic liver disease, people with HIV, people with occupational risk and people with close contact with an international adoptee -- get vaccinated.
Adults without a risk factor who want to avoid hepatitis A infection can also be vaccinated.
"This is important because we don't want this outbreak to grow to the size of the last one," Doron said, referring to the current outbreak in Massachusetts. "Anyone in these categories should be getting vaccinated now and we should be doing all we can to identify people anywhere we see them."
The MDPH said it is working with local health officials and relevant stakeholders to promote and make vaccination available to at-risk populations, including those experiencing homelessness.
Doron and the CDC say another important prevention measure is making sure hygiene and sanitation standards are up to par, including encouraging hand hygiene at facilities that serve high-risk populations and regular disinfection of high-touch surfaces and bathrooms facilities.
Experts also recommend educating high-risk populations and the agencies that serve them on the signs and symptoms of hepatitis A, the need for vaccination and hygiene measures to limit spread.