From NEJM: Full Link: Hepatitis A Outbreak in California — Addressing the Root Cause

On October 13, 2017, Governor Jerry Brown of California declared a state of emergency in response to a hepatitis A outbreak that began in the homeless population in San Diego. In the past year, more than 649 people throughout California have been infected, 417 have been hospitalized, and 21 have died from hepatitis A, making this the largest outbreak in the United States in the past 20 years. The vast majority of those affected have been homeless. Like two thirds of people who experience homelessness in California, most were unsheltered.

The environmental conditions associated with homelessness — overcrowding in encampments and emergency shelters, exposure to the elements, and limited access to facilities for hygiene and food preparation and storage — facilitate infectious-disease transmission..Infectious diseases are one of many health threats faced by homeless people. Poorly controlled chronic diseases, complications of substance use disorders and smoking, and unintentional injuries and violence are prevalent, difficult to manage, and often severe among homeless adults.