incidence: common
cause: virus (hepatitis A)
symptoms: nausea, yellowing of the skin, diarrhea
treatment: none (usually resolves on its own)
Hepatitis A is a virus that causes infection and inflammation of the liver. It has been recognized since the 1960s as a virus distinct from hepatitis B. One often hears of outbreaks of hepatitis A associated with improper food handling in restaurants, but hepatitis A can be transmitted sexually as well, especially through oral-anal contact. So far, hepatitis A and hepatitis B are the only sexually transmitted infections that can be prevented with a vaccination.
HOW COMMON IS IT?
Approximately 30,000 people are diagnosed with hepatitis A each year in the United States, but the Centers for Disease Control estimates that over 100,000 new cases may occur each year in this country. Most of these cases are not the result of sexual transmission. Many people are symptom free or do not seek care for their symptoms.
It is estimated that by the time they reach young adulthood, 15-25 percent of the people in the United States have been infected with hepatitis A, usually by consuming contaminated food or water. As people age, the likelihood that they have acquired hepatitis A increases, with blood tests of more than 75 percent of adults over age seventy showing infection. In the industrialized world, improvements in sanitation have decreased the number of people infected in childhood, whereas in developing countries, where sanitation and water quality may be inadequate, childhood infection is still very common. In many countries, more than 90 percent of children are infected by age five. Infection in childhood may not be a bad thing: most children who become infected with hepatitis A are symptom free, whereas most adults are symptomatic, and although fatalities are rare from hepatitis A, most of the deaths that do occur are in newly infected adults. People who have not been vaccinated or received immune globulin (see the next section) prior to travel to areas of the world where hepatitis A is very common are at increased risk of infection as well.
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