A local public health emergency was first declared by officials on Sept. 1 and signed into law by Regional Health Officer Dr. Wilma Wooten to raise awareness and allow the Health and Human Services Agency to request state assistance if necessary, the San Diego Union-Tribune reports . And on Sept. 6, the San Diego Board of Supervisors unanimously ratified the declaration and discussed new prevention efforts.

The San Diego Board of Supervisors ratified the declaration of a public health emergency on Wednesday as a result of an ongoing outbreak of hepatitis A, an infection that affects the liver.

Since November 2016, the outbreak has infected hundreds of people and left 15 dead — with the homeless population hit the hardest.

According to the San Diego Health & Human Services Agency (HHSA), as of Sept. 5, the current outbreak has infected 398 people, causing 279 hospitalizations.

The San Diego HHSA wrote that the majority of the people who have been infected with the disease are either homeless or illicit drug users, and that the outbreak is being spread between people through contact with a "fecally contaminated environment" — i.e. when an uninfected or unvaccinated person ingests food or water, touches an object, or uses drugs contaminated with fecal matter from an infected person.