1. How is the virus transmitted?

It is spread by the fecal-oral route and is well known to be acquired by eating raw oysters harvested from fecally contaminated water. Filter-feeding shellfish such as oysters, clams, and mussels are believed to concentrate the virus. This patient's history of eating raw oysters 5 weeks prior to the development of hepatitis symptoms is consistent with the incubation period for this virus, which is 2 to 8 weeks.

Because HAV is usually obtained by ingestion of fecally contaminated food or water, good hygiene practices can usually prevent spread of this infection. Since HAV is frequently associated with ingestion of raw shellfish, eating only adequately cooked seafood will eliminate the risk since the virus is inactivated by boiling for 1 min. In outbreak situations, immune globulin is valuable in preventing or suppressing HAV infection. Immune globulin is also given to nonimmune individuals (e.g., Peace Corps workers, missionaries, soldiers, and some tourists) who are traveling to areas of high endemicity which have poor sanitation. Protection in this situation usually lasts for 6 months, and people who remain in these areas for longer than 6 months must receive doses of immune globulin at 6-month intervals.

2. Describe how the HAV infection was detected?

The laboratory diagnosis is a serologic one in which the serum is examined for the presence of anti-HAV immunoglobulin M (IgM) antibodies. The detection of IgM antibodies is necessary because the presence of IgG antibodies to HAV indicates a previous infection at any time in the past. The virus is not cultivable by standard laboratory methods, nor is direct detection of the virus by immunologic or electron-microscopic techniques widely available.

3. Why was liver function so abnormal and then returned to normal? Explain the differences in clinical presentation between adults and children?

After initial replication in the gut, there is viremic spread of the virus to the target tissue (liver). Acute HAV and HBV infections are clinically indistinguishable. HAV infection, as was seen in this case, is generally a benign, self-limited disease. Fulminant hepatitis has been reported with this virus, but is rare. Unlike HBV, HAV does not cause chronic infection and carrier states, nor is it associated with increased risk for hepatic carcinoma.

Children more frequently have asymptomatic infection which they may acquire at day care centers. They are often the source of infection for an adult.

4. What are the long term consequences for HAV infection?

Recovery is generally complete with lasting immunity.

5. There is now a vaccine available for HAV. What type of vaccine is this and who should receive it?

HAV vaccine has recently been licenced by the FDA. This vaccine is inactivated HAV and is very effective in preventing disease. It should be administered to international travelers, children who live in high risk communities (Alaskan Native villages, American Indian reservations, selected other communities) homosexual men, persons with chronic liver disease, and possibly food handlers. Also, it can be used to control an outbreak of hepatitis A in a community.

6. What should be done for household contacts of the patient?

They should receive Immune Globulin.