Louisiana investigating hepatitis A outbreak: What you should know to prevent infection The outbreak makes Louisiana the 15th state to experience an ongoing outbreak.

The Louisiana Office of Public Health is investigating an outbreak of 25 cases of hepatitis A infections, most of which are concentrated in the state capital of Baton Rouge.

Louisiana is the 15th state to declare an ongoing outbreak of the virus, which causes liver disease and is highly contagious, but also preventable with vaccination.

"Compared to what some other states are experiencing, we're quite fortunate and want to keep it that way," Dr. Joe Kanter, assistant state health officer, told the Associated Press. He added that there are 3,122 cases being reported in Kentucky, 561 in Tennessee, 413 in Florida and 217 in Arkansas.

Hepatitis A (HAV) is preventable. Here is everything you should know about it.

HAV is highly contagious and certain populations face a higher risk.

HAV is primarily transmitted through the fecal-oral route, according to the World Health Organization. That means it can be transmitted by making close contact with someone who already has the virus or from food or water that has been contaminated with feces.

“High risk populations include people who abuse drugs, homeless individuals and men who have sex with men. It may also reflect an increase in conditions that lead to spread, such as homelessness or living in unsanitary conditions,” Dr. Kenneth Sands, HCA Healthcare’s chief epidemiologist, told ABC News. “Once the virus gets a foothold in a high-risk population, it will continue to circulate”

The Centers for Disease Control and Prevention says an HAV-infected person can be contagious for up to six weeks, as well as during the two weeks before they begin to show symptoms. This makes identifying people with HAV difficult. Symptoms include fever, fatigue, loss of appetite, nausea, vomiting, abdominal pain, dark urine, clay-colored stool, joint pain and jaundice.

Unlike hepatitis B and C, however, it does not cause chronic liver disease.

There isn’t a cure for hepatitis A, but it’s also rarely fatal.

“The treatment, if you have the disease, is largely supportive care, including hydration, managing symptoms of nausea and abdominal pain,” said Sands.

HAV infections usually resolve without treatment, although they might take several weeks or months to do so, according to WHO. That said, the number of illnesses and deaths associated with the current national outbreaks have been higher than usual due to older age and underlying health conditions — especially chronic liver disease — among those affected.

Hepatitis A infection is a vaccine-preventable illness.

“These outbreaks are a big deal and disappointing” Dr. Todd Ellerin, the chief of infectious disease at South Shore Hospital in Massachusetts, told ABC News, noting that viral infection is preventable with the hepatitis A vaccine.

The Advisory Committee on Immunization Practices (ACIP) recommends routine hepatitis A vaccination for any person wishing to obtain protection from hepatitis A, including children under a year old; travelers to countries where hepatitis A is common; family and caregivers of adoptees from countries where hepatitis A is common; men who have sexual encounters with other men; users of recreational drugs, whether injected or not; and people with chronic or long-term liver disease, including hepatitis B or hepatitis C.

“It is essential that departments of public health work closely with affected communities to provide the vaccine to those who may not have the means to receive it,” Ellerin said, pointing to homeless people and intravenous drug users. “These groups have been disproportionately affected by this infection”

Practicing good hand hygiene — including thoroughly washing hands after using the bathroom, changing diapers and before preparing or eating food — also plays an important role in preventing the spread of hepatitis A, according to the CDC.

Eric M. Strauss (@ericmstrauss) is the managing editor of the ABC News Medical Unit and invites you to follow the unit on twitter @ABCNEWSHEALTH.