West Virginia is contending with one of the nation’s largest hepatitis A virus (HAV) outbreaks in U.S. history, with state health officials reporting 1,031 new cases of the liver virus over the past year. The increase in infections is linked to the state’s ongoing opioid crisis, Scientific American reports.

State records show nearly 80 percent of those infected said they used drugs. Self-reported data indicated that 58 percent of hepatitis A patients used injection drugs, while 42 percent used non-injection drugs, such as methamphetamine and prescription painkillers.

While hepatitis A infections in the United States are typically associated with food-related outbreaks, a growing number of infections have been linked to poor hygiene among Americans struggling with homelessness, which can sometimes accompany addiction. Since hepatitis A is spread through fecal-oral and sexual contact, it is far more likely to spread in communities where bathrooms and showers are scarce.

Meanwhile, West Virginia has been hit hard by the U.S. opioid crisis. Last year, the state had the highest rate of opioid-related overdose deaths in the country. Genetic sequencing of the state’s latest hepatitis A infections indicate West Virginia is fighting the same strain that has struck homeless communities in Kentucky and California. Others at high risk include people who are or have been incarcerated and men who have sex with men.

In response to the rise in new infections, West Virginia health officials have doled out more than 8,000 doses of the hepatitis A vaccine. The state has also requested help from the Centers for Disease Control and Prevention to help slow new transmissions. So far, six federal experts have joined the cause.