By Carol A. Kemper, MD, FACP

Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases, Santa Clara Valley Medical Center

Dr. Kemper reports no financial relationships relevant to this field of study.

SOURCE: 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 Morb Mortal Wkly Rep 2018;67:1208-1210.

A multistate outbreak of hepatitis A virus (HAV) infection in the homeless and/or drug-using population has prompted the United States Advisory Committee on Immunization Practices to add “homelessness” as an indication for HAV vaccination, effective Oct. 24, 2018. This is in addition to existing indications for HAV vaccination of men who have sex with men (MSM) and illicit drug users (with the exception of marijuana use).

During 2017, 1,521 outbreak cases of acute HAV infection were reported in California, Kentucky, Michigan, and Utah, mostly in the homeless and/or drug-using population. An outbreak case was defined as acute HAV infection with a viral specimen matching the outbreak strain or if the case could be linked with another identified case. Although HAV generally is transmitted by close personal or sexual contact and unsanitary conditions, this was the first time an outbreak was fueled in part by parenteral transmission from contaminated needles and other shared paraphernalia. This shift in the epidemiology of HAV infection raised alarms for health officials.

Forty-one of outbreak cases died and 1,073 were hospitalized. Three percent had confirmed hepatitis B coinfection and 22% had confirmed or probable hepatitis C coinfection. Fifty-seven percent reported homelessness and/or drug use, and 5% were MSM.

Increasingly, molecular techniques are used to identify outbreaks of HAV infection. For this investigation, serum samples submitted to the CDC were used to extract and amplify a fragment of the VP1/P2B region of the virus for genetic characterization. A total of 1,054 specimens were tested, 96% of which were positive for genotype 1b virus, which generally is an uncommon strain. Most clinical cases of HAV infection in the United States before 2017 have been due to genotype 1a virus. The genotype 1b strain circulating in California, Utah, and Kentucky was different from that found in Michigan.

In California, the outbreak started in San Diego County in November 2016 and quickly spread to Los Angeles, Santa Cruz, and Monterey counties. In October 2017, Gov. Jerry Brown declared a state of emergency to secure many vaccine doses. Three California counties mounted an offensive, deploying vans to homeless encampments and distributing alerts to local clinics and emergency rooms. Approximately 123,000 doses of HAV vaccine were dispensed, effectively quelling the outbreak.

Although aggressive public health intervention in California stopped the outbreak there, it continues in Kentucky, Michigan, and Utah and may be spreading to other states. As of October 2018, more than 7,000 cases of acute HAV infection have been reported from 12 states.