The U.S. state of California is experiencing the largest person-to-person outbreak of Hepatitis A in the United States since a vaccine to prevent the liver disease became available in 1996.
More than 600 cases have been reported in the state and 21 people have died. According to the California Department of Public Health, most of those infected are homeless or use drugs in places where sanitation has been a challenge.
An area in downtown Los Angeles is known for its homeless population. A recent study found that the area fell short of U.N. refugee camp standards calling for one public toilet for every 20 people.
Analysts say unsanitary conditions can become a breeding ground for the hepatitis A virus.