Hepatitis A Outbreaks in the United States

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Current Outbreak

Background

In recent years, hepatitis A outbreaks have occurred from several different sources:

  • Foodborne transmission through ingestion of contaminated food
  • Person-to-person transmission through close contact with an infected person, most recently, among people who use drugs, people experiencing homelessness, and men who have sex with men.
Current Outbreaks

In 1996, the Advisory Committee on Immunization Practices (ACIP) first made recommendations to prevent hepatitis A through immunization, focusing primarily on vaccinating people in groups shown to be at high risk for infection and children living in communities with high rates of disease. In 2006, ACIP started recommending routine hepatitis A vaccination of children nationwide. Recent outbreaks have mainly affected adults. Increased vaccination efforts targeting adults in at-risk populations can help limit the size, duration, and spread of person-to-person outbreaks. CDC has updated its overall recommendations on the prevention of hepatitis A virus infection in the United States.

Hepatitis A Cases in the United States

Fluctuations in the reported cases have occurred in the last 20 years due to large outbreaks. After a long downward trend, the first increase between 2012 and 2013 (1,562 and 1,781 reported cases, respectively), was due to a large multi-state outbreak associated with pomegranate arils imported from Turkey. Between 2015 and 2016, the reported cases again increased from 1,390 in 2015 to 2,007 cases in 2016. The 2016 increase was due primarily to two foodborne hepatitis A outbreaks, each of which was linked to contaminated imported foods. Substantial increases in incident cases of hepatitis A have occurred since late 2016 through 2019 (3,366, 12,474, and 18,846 reported cases in 2017, 2018, and 2019, respectively) due to ongoing outbreaks reported to CDC among people who use drugs and people experiencing homelessness.

Reported cases began declining in 2020. During 2021, the number of reported cases was 5,728. The number of reported cases during 2021 corresponds to a 43% decrease from 2020 but remains four times the number reported during 2015, before the hepatitis A outbreaks associated with person-to-person transmission were first reported. During 2021, eight states declared an end to their outbreaks. Disruptions to healthcare access and health department surveillance capacity during the COVID-19 pandemic may have affected the ability to detect and report all hepatitis A cases in 2020 and 2021. In 2022 and 2023 there were multistate outbreaks linked to imported organic strawberries.

CDC’s role in responding to hepatitis A outbreaks

State and local health departments typically lead the investigations of local outbreaks of hepatitis A.  When requested by the health department, CDC can support health departments in these investigations by:

  • Communicating with public health officials from states with reported cases and providing technical assistance;
  • Gathering data reported by states on confirmed cases and evaluating and monitoring these data from a national perspective;
  • Providing support on vaccine supply and distribution and vaccine response strategy development;
  • Testing clinical specimens from suspected hepatitis A cases when requested by states;
  • Providing technical assistance and answering questions related to molecular and serologic laboratory testing;
  • Providing rapid assistance on the ground during outbreak investigations, often through a formal request by the state health department;
  • Alerting clinicians, health care facilities, and public health officials around the country about current outbreaks and providing vaccine policy and clinical guidance for health care providers; and
  • Providing information to public and health care providers through a variety of media.

Previous hepatitis A outbreak investigations

For a comprehensive listing of reported foodborne hepatitis A outbreaks, see the National Outbreak Reporting System (NORS) Online Database tool, check the box for “Foodborne,” and under the etiology search option, select “hepatitis.”

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