Hepatitis A (formerly known as ''infectious hepatitis'') is an acute infectious disease of the liver caused by the hepatitis A virus (HAV), which is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. Every year, approximately 10 million people worldwide are infected with the virus. The time between infection and the appearance of the symptoms, (the incubation period), is between two and six weeks and the average incubation period is 28 days.
In developing countries, and in regions with poor hygiene standards, the incidence of infection with this virus is high and the illness is usually contracted in early childhood. HAV has also been found in samples taken to study ocean water quality. Hepatitis A infection causes no clinical signs and symptoms in over 90% of infected children and since the infection confers lifelong immunity, the disease is of no special significance to the indigenous population. In Europe, the United States and other industrialized countries, on the other hand, the infection is contracted primarily by susceptible young adults, most of whom are infected with the virus during trips to countries with a high incidence of the disease.
Symptoms can return over the following 6–9 months and include:
- Abdominal pain
- Appetite loss
- Jaundice, a yellowing of the skin or whites of the eyes
- Sharp pains in the right-upper quadrant of the abdomen
- Weight loss
- Bile is removed from blood stream and excreted in urine giving a dark amber colour
- Feces tend to be light in colour due to lack of bilirubin in bile
The Hepatitis virus (HAV) is a Picornavirus; it is non-enveloped and contains a single-stranded RNA packaged in a protein shell. There is only one serotype of the virus, but multiple genotypes exist.
Following ingestion, HAV enters the bloodstream through the epithelium of the oropharynx or intestine. The blood carries the virus to its target, the liver, and multiplies within hepatocytes and Kupffer cells (i.e., liver macrophages). There is no apparent virus-mediated cytotoxicity, and liver pathology is likely immune-mediated. Virions are secreted into the bile and released in stool. HAV is excreted in large quantities approximately 11 days prior to appearance of symptoms or anti-HAV IgM antibodies in the blood. The incubation period is 15–50 days, and mortality is less than 0.5%.
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