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Public Health - Seattle & King County

Hepatitis A

Hepatitis A virus (HAV) infects the liver. It is primarily acquired via the fecal-oral route, either through person-to-person contact or by ingestion of fecally-contaminated food or water. Before routine childhood vaccination against hepatitis A, infection was common among children. Today adults account for the majority of cases. Most cases occur through consumption of contaminated food during travel. Hepatitis A has also been linked to sexual activity among men who have sex with men when oral contact with stool-contaminated skin occurs. Illicit drug users are also at higher risk of hepatitis A. Unlike hepatitis B or C, HAV does not cause chronic infection or carriage. HAV is more common in developing countries where sanitation is poor and vaccine is not available.

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Hepatitis A in King County

Purpose of surveillance:

  • To identify persons exposed to cases of hepatitis A so that preventive treatment can be administered
  • To identify common source outbreaks
  • To identify and eliminate sources of transmission including contaminated food and water

Hepatitis A case data

Local epidemiology:

Ten cases of hepatitis A were reported in 2012, all of which were in adults age 18 and over. Four cases were associated with international travel to Asia (1 case), Mexico (1 case) or Central and South America (2 cases). Three cases had no identified risk factors, two cases required hospitalization, none died.

One case occurred in a recent immigrant from Asia. A cluster of three cases occurred within an extended family living in two households. The index case had traveled to Mexico during the exposure period; following the case's return, two family members for whom the case had prepared food during the infectious period developed hepatitis A. One of the exposed family members had refused recommended preventive treatment and the other had not been reported as a close contact of the case during the initial investigation.. In 2011, a cluster of nine cases occurred among methamphetamine injection drug users and their contacts in East King County; one additional linked case lived in another county. The first case in the cluster was likely exposed while traveling to Mexico.

Prior to the introduction of hepatitis A vaccine in 1995, hundreds of cases occurred every year in King County, with cyclical peaks approximately every five years. Since the introduction of hepatitis A vaccine in 1995, cases have progressively declined locally and nationally.