Louisville is the epicenter of a hepatitis A virus (HAV) outbreak in Kentucky. The Southern city has reported some 115 acute cases of the liver virus since November 2017, USA Today reports.

As in previous cities that have experienced outbreaks this year, including San Diego, Salt Lake City and Detroit, local health officials are moving quickly to vaccinate those at highest risk for infection and scrambling to determine how the virus began to spread.

According to a spokesman from the Louisville Department of Public Health and Wellness, the city typically gets just four to five new cases of hepatitis A every year. In 2018, that number is 23 times higher than average, likely due to a nationwide outbreak that continues to strike cities across the country.

One potential cause of this most recent outbreak is an employee at a Louisville Kroger supermarket who tested positive for HAV. His diagnosis prompted the grocery chain to issue an official alert this month to anyone who bought produce between February 4 and 28 at one of its Dixie Highway locations.

Louisville officials say more than 5,700 people across the city have been vaccinated since the outbreak began. Statewide, Kentucky has reported 125 cases total and no deaths.

Those considered to be at a high risk for infection or for spreading the virus include low-income families (who may not have been vaccinated), drug users and homeless or transient people. Officials say several Louisville inmates have also tested positive for hepatitis A, which has led to a series of vaccinations and cleanings at local jails.