Hepatitis A Outbreaks in Certain States Linked to Drug Use, Homelessness

The epidemiology of hepatitis A has shifted from point-source outbreaks to outbreaks caused by person-to-person transmission.

A new report published in the CDC Morbidity and Mortality Weekly Report (MMWR) has linked cases of acute hepatitis A virus (HAV) infections from certain states to person-to-person transmission from drug use or homelessness.

According to the CDC, HAV incidence in the United States steadily decreased after the hepatitis A vaccine was introduced, but stabilized at an annual average of approximately 1600 cases. Outbreaks typically occur among international travelers returning from countries with endemic HAV or foodborne outbreaks, but can also be spread through injection drug use and conditions associated with homelessness.

The MMWR analysis showed that investigations conducted by local and state health departments pointed to direct person-to-person transmission for sustained HAV infections in certain states. According to the report, a total of 1521 outbreak-associated HAV cases were reported from California, Kentucky, Michigan, and Utah in 2017. Among states reporting increases in HAV infection to the CDC, only these 4 states reported sustained within-state transmission.

In the United States, transmissions associated with needle-sharing dropped after the hepatitis A vaccine was recommended for individuals who use illicit drugs. The Advisory Committee on Immunization Practices (ACIP) also recently voted unanimously to add “homelessness” as an indication for ACIP-recommended HAV vaccination.

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However, vaccination rates among identified risk groups are believed to be low, according to the CDC. The report’s authors indicated that outbreaks in these affected populations are typically more difficult to control due to issues such as transient housing, economic instability, limited access to health care, and distrust of government services.

Of the reported cases, there were 1073 hospitalizations and 41 deaths. Among the patients for whom clinical or laboratory records were available, 3% had confirmed or probable hepatitis B virus coinfection and 22% had confirmed or probable hepatitis C virus coinfection.

Additionally, the data showed that 57% of patients reported drug use, homelessness, or both. Fifty-four percent of patients had an indication for HAV vaccination before becoming infected, according to the study. The report also noted that the strains circulating in California, Kentucky, and Utah were genetically different from those circulating in Michigan.

The shifting epidemiology from point-source outbreaks associated with contaminated food consumption to community-wide outbreaks from person-to-person transmission underscores the need to adjust targeted public health efforts. Increasing vaccination coverage among all at-risk groups recommended by ACIP may help stop ongoing outbreaks and prevent future large community outbreaks, the authors concluded.


Foster M, Ramachandran S, Myatt K, et al. Hepatitis A Outbreaks Associated with Drug Use and Homelessness — California, Kentucky, Michigan, and Utah, 2017. MMWR. 2018. https://www.cdc.gov/mmwr/volumes/67/wr/mm6743a3.htm?s_cid=mm6743a3_w