In good times, hepatitis A cases in Philadelphia are relatively unusual. The city had a five-year average of nine cases annually, as of 2017.

This isn’t one of the good times. Thus far, in 2019, they’ve seen 176 cases. One person has died.

“We’re seeing numbers like we saw before the vaccine was really in use,” said Dana Perella, acute communicable disease program manager for Philadelphia’s Department of Public Health.

The city declared a public health emergency due to the outbreak on August 2.

Philadelphia isn’t alone. Since 2016, a rash of hepatitis A outbreaks have been springing up in at least 29 states across the country. Current episodes are as far-flung as Arizona and New Hampshire. More than 230 people have died.

A vaccine for the disease has been available since 1995, and children receive the vaccine beginning at 12 months. It’s not standard procedure to give it to adults, although some communities affected by hepatitis A are trying to get ahead of the disease by vaccinating at-risk adults.

Because hepatitis A is spread through contact through even traces of fecal matter, and occasionally by sharing needles, certain populations are more vulnerable, including people who use intravenous drugs or experience homelessness.

In Philadelphia, drugs and homelessness appear to be primary factors driving the outbreak forward. 68% of people who have been infected with the virus are reporting past drug use, according to preliminary analysis. About 26% are homeless.

“We have this population we know is at risk,” Perella said. “With individuals who are both living with drugs and individuals who are living homeless, lacking sanitation facilities, lacking handwashing facilities, is going to make this spread more quickly.”

In an effort to stop the disease from spreading, Philadelphia’s Department of Public Health has launched street vaccination campaigns and partnered with a needle exchange program to get people who use drugs vaccinated.

The city is also reaching out to the sexual partners and household members of people diagnosed with the disease, to provide preventative measures.

“The main thing is to really galvanize our partners in the health community to help out with this response,” said Perella. “We know we’re not going to be able to do this alone.”

As part of its response to the outbreak, the Department of Public Health asked Direct Relief to send a supply of Gamastan, a medication that provides protection against some viral infections (including hepatitis A, measles, and chickenpox), and is given to people who have experienced possible exposure.

The city plans to use Gamastan to protect immunocompromised people who may have been exposed to the disease, and to distribute it to emergency departments that focus on children. They’re concerned about children under the age of one, who are too young to receive a hepatitis A vaccination, as well as adults who are too old to have received a vaccination in childhood.

“We have folks that don’t have immunity to the virus,” Perella said. “It’s just making conditions ripe for an outbreak.”