A fifth person has died amid San Diego County’s ongoing hepatitis A virus (HAV) outbreak, which started in November and has since grown at an alarming rate among the region’s homeless population, The Los Angeles Times reports.

According to the county’s Health and Human Services Agency latest update on the outbreak, there have been 228 confirmed cases of the liver virus so far, and 161 people have been hospitalized as a result of infection. Although health investigators have not yet discovered the source of the outbreak, they have noted that about 70 percent of the confirmed cases have involved homeless people and that their inability to access proper sanitation is the most likely culprit.

Hepatitis A, which can pass from person to person through shared food, drink, drugs and other forms of close contact can be prevented through vaccination, which has so far been the county’s main strategy for curbing the outbreak. Several local nonprofits that serve the homeless have been operating free HAV vaccination clinics since the spring. In recent weeks, public health workers have also formed “foot teams” to visit people in the streets and in public parks to urge them to get vaccinated.

Still, the number of reported hepatitis A infections throughout San Diego county appears to have more than tripled since May 2017. Health officials say tracking the hep A outbreak has been difficult, as most infected patients interviewed at the hospital do not appear to have fixed addresses. What’s more, anyone age 23 or older was born before the hepatitis A vaccine was available and may not be protected from the virus.

In addition to getting a preventive shot, public health authorities also said people should be sure to wash their hands for at least 20 seconds with soap and running water before eating and after using the bathroom to avoid the spread of infection. San Diego county residents have also been advised to avoid directly touching bathroom door handles when exiting public restrooms and to avoid sharing food, beverages or smoking materials with others.

Finally, county officials have indicated that they are considering a proposal to install public hand-washing stations and to distribute sanitation kits among the homeless to help stop the spread of hepatitis A.