Hepatitis, Viral, Type A

Description

Hepatitis A is a viral infection of the liver caused by hepatitis A virus (HAV). The clinical manifestations of HAV infection range in clinical severity from no symptoms to a mild illness lasting 1–2 weeks to a severely disabling disease lasting several months. Clinical manifestations of hepatitis A often include fever, malaise, anorexia, nausea, and abdominal discomfort, followed within a few days by jaundice.

Occurrence

HAV is shed in the feces of persons with HAV infection. Transmission can occur through direct person-to-person contact; through exposure to contaminated water, ice, or shellfish harvested from sewage-contaminated water; or from fruits, vegetables, or other foods that are eaten uncooked and that were contaminated during harvesting or subsequent handling.

HAV infection is common (high or intermediate endemicity) throughout the developing world, where infections most frequently are acquired during early childhood and usually are asymptomatic or mild. In developed countries, HAV infection is less common (low endemicity), but communitywide outbreaks still occur in some areas of the United States.

Risk for Travelers

The risk of acquiring HAV infection for U.S. residents traveling abroad varies with living conditions, length of stay, and the incidence of HAV infection in the area visited. Travelers to North America (except Mexico), Japan, Australia, New Zealand, and developed countries in Europe are at no greater risk for infection than in the United States. For travelers to low-income countries, risk for infection increases with duration of travel and is highest for those who live in or visit rural areas, trek in back country areas, or frequently eat or drink in settings of poor sanitation. Nevertheless, many cases of travel-related hepatitis A occur in travelers to developing countries with “standard” tourist itineraries, accommodations, and food consumption behaviors.

Clinical Presentation

The incubation period for hepatitis A averages 28 days (range 15–50 days). Hepatitis A typically has an abrupt onset of symptoms that can include fever, malaise, anorexia, nausea, abdominal discomfort, dark urine, and jaundice. The likelihood of having symptoms with HAV infection is related to the infected person's age. In children <6 years old, most (70%) infections are asymptomatic; if illness does occur it is not usually last <2 months. There is no chronic or long-term infection associated with hepatitis A, but 10% of infected persons will have prolonged or relapsing symptoms over a 6- to 9-month period. The overall case-fatality rate among cases reported to CDC is 0.3%; however, the rate is 1.8% among adults >50 years of age.

Prevention

Hepatitis A is one of the most common vaccine-preventable diseases in travelers. Hepatitis A vaccine, immune globulin (IG), or both, are recommended for all susceptible persons traveling to or working in countries with an intermediate or high endemicity of HAV infection.

For maximum protection, Hepatitis A vaccination should be given 4-weeks before first travel to countries with high or intermediate endemicity.  One month after receiving the first dose of monovalent hepatitis A vaccine, 94%–100% of adults and children will have protective concentrations of antibody. The final dose in the hepatitis A vaccine series is necessary to promote long-term protection. Many persons will have a detectable antibody to hepatitis A virus (anti-HAV) response to the monovalent vaccine by 2 weeks after the first vaccine dose.