Hepatitis A Among People Who Use Drugs or Are Homeless: Four State Outbreaks, 2017

This page describes outbreaks reported in 2017 and the situation as of October 2018.

Hepatitis A is a vaccine-preventable liver infection, usually spread by swallowing tiny amounts of feces. U.S. outbreaks had been uncommon and were typically traced to contaminated food. In 2017, that changed. California, Kentucky, Michigan and Utah reported 1,521 cases of acute hepatitis A infection, most among people who used drugs, whether by injection or not, or who were homeless. Local and state investigators found the virus passing directly from person to person, a shift from the large recent outbreaks caused by contaminated commercial foods.

The report on these outbreaks was written by CDC with the health departments of Kentucky, Michigan and Utah and San Diego County.

The cases

Cases met the 2012 national definition of acute hepatitis A, matched an outbreak strain, or were linked to a known case. Health department staff reviewed charts and interviewed patients about drug use, sexual history, housing, travel and contact with other patients. Only these four states had sustained transmission within the state; cases elsewhere traced to travel to them were excluded.

For comparison, in 2016 the national hospitalization and death rates for hepatitis A were 42% and 0.7%. The higher rates in 2017 may reflect other illnesses, including chronic hepatitis B and C, age, and risks common among people who use drugs or are homeless, such as heavy drinking.

The virus

CDC's Division of Viral Hepatitis received 1,169 specimens from the four states. Hepatitis A was confirmed by PCR in 1,054 (90%), and 1,014 (96%) of those were genotype 1b. The strains in California, Kentucky and Utah were genetically different from Michigan's. Before 2017, most specimens CDC tested were genotype 1a, the most common in the Americas, so the outbreaks were bringing a previously uncommon genotype to the fore. Combined with good epidemiologic data, such laboratory work helps map transmission, especially among people wary of investigators.

The response

CDC worked with health departments on advisories, public education and vaccination clinics aimed at the people most at risk. Vaccine was given in jails, emergency departments, syringe exchange programs, drug treatment centers and homeless shelters, and some teams went into homeless encampments to educate and vaccinate. California's outbreak had ended by the time of the report, but new cases were still being investigated in Kentucky, Michigan and Utah, and vaccination campaigns continued.

Why it happened

After hepatitis A vaccine arrived in 1996, reported infections fell steadily until 2011, then leveled off at about 1,600 cases a year, mostly in travelers returning from countries where the virus is common or in foodborne outbreaks. Outbreaks among people using illicit drugs had been common before the vaccine; in the mid-1980s they made up more than 20% of reported cases. But large community outbreaks in this group became rare after 1996, when the vaccine was first recommended for people who use illicit drugs.

Among people who use drugs or are homeless, the virus can spread through unsanitary conditions, certain sexual practices, or contaminated needles and other injection equipment. Unstable housing, economic hardship, poor access to health care and distrust of government make these outbreaks hard to control and call for public health efforts tailored to people's circumstances.

Vaccination rates in groups already recommended for vaccine were unknown but believed to be low. On October 24, 2018, the Advisory Committee on Immunization Practices voted unanimously to add homelessness as a reason for hepatitis A vaccination. As of October 12, 2018, more than 7,000 outbreak-associated cases had been reported from 12 states.

CDC advised health departments facing such outbreaks to make sure drug use and homelessness are identified and those groups vaccinated, and asked that any new suspected clusters be reported to state and local health departments and CDC. Raising vaccination among all at-risk groups might stop ongoing outbreaks and prevent large ones in future.

Sources

• Foster M, Ramachandran S, Myatt K, et al. "Hepatitis A Virus Outbreaks Associated with Drug Use and Homelessness — California, Kentucky, Michigan, and Utah, 2017." MMWR 67(43). https://www.cdc.gov/mmwr/volumes/67/wr/mm6743a3.htm
• CDC outbreak page: https://www.cdc.gov/hepatitis/outbreaks/2017March-HepatitisA.htm; health advisory: https://emergency.cdc.gov/han/han00412.asp