Updated: May 30, 2018 2:15 PM ET | Originally published: May 30, 2018 9:20 AM EDT

Ohio has joined a growing number of states battling hepatitis A outbreaks, public health officials report.

The state has already seen 79 cases of hepatitis A this year, nearly twice as many as were reported in all of 2017, Cleveland.com reports. The uptick led the Ohio Department of Public Health to declare a statewide hepatitis A outbreak on Friday, according to Cleveland.com.

The announcement comes about a month after the Nashville Metro Public Health Department (MPHD) announced that 14 cases of hepatitis A had been confirmed in the city since December 2017 —significantly more than the two cases it sees in an average year. MPHD is working with state public health officials to contain the outbreak, according to a statement, but the infection has already popped up in a number of nearby states, as well as some on the West Coast.

Here’s what to know about hepatitis A and the outbreaks around the country.

What is hepatitis A?

Hepatitis A is an acute viral infection that causes inflammation of the liver, resulting in symptoms such as fatigue, appetite loss, nausea, stomach pain and jaundice, according to the Centers for Disease Control and Prevention (CDC). The disease is typically spread through close contact with an infected person, or by eating or drinking contaminated food or water. Symptoms typically go away within two months, the CDC says, but patients may develop liver failure or other complications. In some cases, the disease can be fatal.

Thanks to the efficacy of the hepatitis A vaccine, the CDC reports that rates of the disease have dropped by 95% since 1995 — which makes the current outbreaks somewhat unusual.

Which states are experiencing hepatitis A outbreaks?

At least nine states have experienced recent hepatitis A outbreaks: Ohio, Tennessee, California, Indiana, Kentucky, Michigan, Utah, Arizona and West Virginia. The outbreaks in Michigan and California appear to be the most widespread. A total of 837 cases have been reported in Michigan since May 2016, and California saw 704 cases between November 2016 and the end of its outbreak in April 2018.

The CDC said most of these states have seen genetically similar or identical strains of hepatitis A, CNN reports.

What’s behind these hepatitis A outbreaks?

People who use drugs, men who have sex with men and homeless individuals are at heightened risk of developing hepatitis A, and those factors seem to be at work in many of the current outbreaks. Public health officials in California, Indiana, Michigan and Utah have highlighted these risk factors, and Arizona’s outbreak was largely confined to homeless individuals who sought services at the same shelter. Nashville is also offering free vaccines to drug users and men who have male sexual partners.

In some cases, the disease can also be traced to a common source of exposure. Earlier this year, for example, as many as 2,000 people were exposed to the virus at a Utah 7-Eleven, and frozen strawberries were blamed for an outbreak in 2016.

How can you protect yourself from hepatitis A?

The first step is making sure you’ve been vaccinated. The CDC recommends that all one-year-old children get the shot, as well as adults who may be at heightened risk of contracting the disease. And while there were some vaccine shortages reported in 2017, the CDC says supplies of both adult and pediatric hepatitis A vaccines are able to meet current demand.

Hand-washing, proper hygiene and following food safety guidelines can also help cut down on transmission, the CDC says.

Write to Jamie Ducharme at jamie.ducharme@time.com.

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