Hepatitis A virus (HAV) is a ribonucleic acid-containing virus that causes acute viral hepatitis. Infection with hepatitis A virus, unlike infection with viral hepatitis B, C, or D, causes only an acute illness that is usually self-limited. HAV does not lead to either chronic hepatitis or a carrier state.
The disease is spread mainly by the fecal-oral route or by exposure to fecally contaminated food and water. Most persons are infected by contact with a person with hepatitis; male sexual activity involving sex with other men; foreign travel to developing regions or regions with poor sanitation, including Africa, the Middle East, Asia, and Central and South America; contact with infected children attending day care centers; or illicit drug use. Rarely, the disease is transmitted via transfusion of blood products from a donor who gave blood during the viral incubation period.
Person-to-person transmission is responsible for most of the transmission of hepatitis A. Contaminated produce, water, and food (particularly shellfish) continue to cause common-source outbreaks. Transmission of hepatitis A within families is common.
In the United States, national rates of hepatitis A have tended to fluctuate in cycles, with an increase in the number of reported cases occurring every 10 years. In 1992, over 21,000 cases of viral hepatitis A were reported in the United States by the Centers for Disease Control and Prevention (CDC), but the incidence of infection is estimated to be several times higher. Since 1983, the age-specific rates have not been significantly different.
Outbreaks of hepatitis A among drug users have been recently reported. The Centers for Disease Control and Prevention (CDC) has proposed two possible explanations for this occurrence. One explanation is that HAV is being transmitted by injection or ingestion of contaminated drugs, and the other is that HAV is being spread by person-to-person transmission as a result of sharing needles, sexual contact, or poor sanitary and personal hygiene conditions.
In children and young adolescents, about 80 percent of infected people are asymptomatic and have no jaundice. In the adult population, jaundice usually occurs after an incubation period of 15 to 40 days; it may be associated with fever and diarrhea. Hepatitis A is a self-limited illness in most cases. Relapsing hepatitis or cholestatic hepatitis may occur in a small number of cases, but fulminant hepatitis is rare.
Drug users are considered a population at high risk for hepatitis A. Several seroepidemiologic studies have shown higher rates of viral hepatitis A antibody among drug users than in the general population; hepatitis A is a marker for injection drug use among young adults.
There is no need to conduct routine serologic screening to establish prior HAV exposure. However, the following screening and prevention procedures should be done:
Serologic screening is appropriate for persons with jaundice.
Persons should be screened for HAV infection if they have clinical manifestations of acute hepatitis or intimate contact with a person with known acute HAV infection.
Post-exposure prophylaxis with immune serum globulin should be given to persons exposed to HAV who have had no prior HAV infection (i.e., are anti-HAV negative).
Health care workers should be screened for HAV only if they have known intimate contact exposure or symptoms of acute viral hepatitis.
Persons enrolled in drug treatment programs should be educated about the way that this and other hepatitis viruses spread. Behaviors that place persons at risk for HAV infection include having unprotected sex, injecting drugs, having multiple injection-drug partners, sharing or using contaminated drug paraphernalia, using commode water as a diluent for drugs, smuggling drugs rectally, and having poor personal hygiene.
Reporting of HAV to local and State health departments is required and should be done in a timely manner to prevent or limit a community outbreak of hepatitis A.
After exposure to hepatitis A virus, the incubation period prior to the development of clinical manifestations of infection is usually 28 to 30 days. Infected persons are contagious before the development of overt signs and symptoms.
The most common manifestations of infection are fatigue, jaundice, dark urine, and light-colored stools. Other symptoms include loss of appetite, distaste for cigarettes, nausea, vomiting, and abdominal pain; less common symptoms are fever, chills, headache, muscle pain, joint pain, and diarrhea. These clinical manifestations, combined with elevated liver aminotransferases, aspartate aminotransferase (AST), and alanine aminotransferase (ALT), are consistent with viral hepatitis. The definitive diagnosis of acute viral hepatitis A is made by the serologic presence of immunoglobulin M (IgM) anti-HAV (representative of acute infection within the past 6 to 12 months). Past exposure can be diagnosed by the presence of immunoglobulin G (IgG) anti-HAV.
Once a person has been infected with HAV, protective immunity is long lasting.
For most infected persons, the acute illness lasts from 1 to 3 weeks. However, it may take some time for all symptoms to resolve. HAV infection does not cause chronic disease; a year after acute hepatitis, liver enzymes should be normal.
Some infected persons may have cholestatic jaundice or relapsing hepatitis A. Rarely, patients may develop fulminant and even fatal hepatitis.
There is no specific treatment for hepatitis A other than treating its symptoms. In general, patients should reduce their level of activity. Bed rest may be appropriate in the initial stages, but studies have shown that normal activities, and even heavy physical exercise, do not alter the course of the disease during the recovery period. Alcohol should not be consumed during the acute phase.
Some persons may have a prolonged period of jaundice, for up to 12 weeks, complicated by diarrhea, weight loss, and pruritus. Such persons should be under the supervision of a physician knowledgeable about HAV. Persons with fulminant hepatitis A infection require hospitalization and intensive supportive care. Fulminant hepatitis is usually fatal.
Persons with no prior HAV infection (i.e., anti-HAV negative) who are known to have been exposed to HAV should be given immune serum globulin (ISG). A dose of 0.02 ml/kg of ISG should be given as soon as possible, but within no more than 2 weeks of the exposure.
Since there is no currently licensed vaccine for HAV, preventing the spread of this virus depends on the maintenance of high standards of hygiene.
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