Hepatitis A Outbreaks in the United States

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.

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.

Hepatitis A Cases in the United States

Graph with years 2001 through 2016 along x axis and number of cases along the Y axis. Charted cases declines from a high of about 10,300 cases in 2001 to about 2,000 in 2016.

Source: CDC, National Notifiable Diseases Surveillance System (NNDSS)

While the average number of annual hepatitis A virus (HAV) infections reported to CDC in recent years has declined substantially compared to 2000, fluctuations have occurred in the last 20 years because large outbreaks occurred. 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 by 44.4% from 1,390 in 2015 to 2,007 cases in 2016. The 2016 increase was due to two hepatitis A outbreaks, each of which was linked to imported foods. Routine surveillance data on incident cases from 2017 and 2018 are not yet available but increases are expected due to ongoing outbreaks reported to CDC among people who use drugs and people experiencing homelessness as well as outbreaks among men who have sex with men.

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, healthcare facilities, and public health officials around the country about current outbreaks and providing vaccine policy and clinical guidance for healthcare providers; and
  • Providing information to public and healthcare 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 “Food,” and under the etiology search option, select “hepatitis.”

Resources