Medical Definition of Hepatitis A
Hepatitis A: Inflammation of the liver caused by the hepatitis A virus (HAV). HAV is usually transmitted from person to person by food or drink that has been contaminated with the stool of a person with hepatitis A. This type of transmission is called "fecal-oral." The virus is more easily spread in areas where there are poor sanitary conditions or where good personal hygiene is not observed. In 2003 there were hepatitis A outbreaks in the US associated with eating raw or lightly cooked green onions (scallions). Casual contact, as in a school, office, or another work setting, does not spread the virus.
Hepatitis A can be transmitted by men (both adolescents and adults) who have sex with men. Hepatitis A outbreaks among men who have sex with men have been frequently reported. The virus can also be transmitted by illegal-drug users.
Hepatitis A develops within 2 months of exposure to the virus. The average incubation period for the virus is 28 days (range: 15-50 days) until symptoms appear. Hepatitis A can range greatly in severity. Some persons with hepatitis A virus infection have no signs or symptoms of the disease. Older persons are more likely to have symptoms than children. In its most dire form, the disease can lead to liver failure and death. This is relatively rare.
The symptoms and signs tend to appear abruptly and may include fatigue, loss of appetite, nausea, diarrhea, abdominal pain, fever, and jaundice (yellowing of the skin and eyes) and dark urine. Symptoms usually last less than 2 months. A few persons are ill for as long as 6 months. Recovery is usually complete.
The diagnosis of hepatitis A is confirmed by a blood test (IgM anti-HAV). When immediate protection against hepatitis A infection is needed, immunoglobulin (gamma globulin) is used. Immunoglobulin is effective only if given within two weeks of exposure, and protection only lasts for two to four months. Immunoglobulin can be used to protect household contacts of someone with acute viral hepatitis, and by travelers who must depart for regions with poor sanitation and high hepatitis A rates before vaccines can take effect. Travelers can receive immunoglobulin and hepatitis A vaccine simultaneously.
Hepatitis A vaccine is used before exposure to hepatitis A virus for persons who are more likely to get the infection or are more likely to get seriously ill if they do get hepatitis A. The Centers for Disease Control & Prevention (CDC) recommend the hepatitis A vaccine for persons traveling to or working in countries that have high or intermediate rates of hepatitis A; children in areas where the rates of hepatitis A were or are at least twice the national average during the baseline period of 1987-1997; men who have sex with men; injecting and non-injecting illegal-drug users; persons who work with hepatitis A virus-infected primates or with hepatitis A virus in a research laboratory setting; people with chronic liver disease; and persons who have clotting-factor disorders such as hemophilia and who are administered clotting-factor concentrates such as Factor VIII and Factor IX.
Also called infectious hepatitis, epidemic jaundice. See also hepatitis A immunization.
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