Hepatitis A is one of the most common human infections. The infective agent of disease is hepatitis A virus (HAV), belonging to the family Picornaviridae. Viral genome is represented by (...)
Hepatitis A is one of the most common human infections. The infective agent of disease is hepatitis A virus (HAV), belonging to the family Picornaviridae. Viral genome is represented by single-strand RNA. Feature of hepatitis A virus is its stability in the environment: at room temperature it can remain viable for several weeks or months, and at 4 °C – for a few months or years. Only thermal inactivation at 100 °C for 5 minutes can destroy the virus.
Annually about ten million people in the world are infected with hepatitis A virus. Children and adolescents may have asymptomatic hepatitis A; the disease is severer for babies and seniors. For adults, the infection often occurs with severe intoxication and jaundice. The duration of the disease depends on the immune system, the person’s age and other factors, but on average it takes about 40 days. 15% of patients have a chronic form of hepatitis A in the course of 6 to 9 months. The risk of death from the disease ranges from 0,1 to 2,4% for people older than 40 years. Full recovery is observed for 90% of patients, in other cases there are residual effects.
The source of infection is a person sick of hepatitis A who excretes with faeces billions of viruses into environment. With contaminated water and food the virus enters the intestine, penetrate the epithelial wall and get into the bloodstream and penetrate the liver and its cells - hepatocytes and Kupffer cells. After virus replication cells are destroyed by its cytolytic action, resulting in the development of inflammation and abnormal liver function. Viral particles are secreted into bile and excreted by defecation (with stools). On average, viral particles are excreted in significant amounts for about 11 days before the emergence of symptoms or IgM class antibodies against hepatitis A virus emergence in the blood. The incubation period for hepatitis A lasts 15 to 50 days. IgM class antibodies appear 3-5 days before the first symptoms and store in the patient’s blood for 3-6 months, decreasing to low levels for the year. The nascence of IgG antibodies indicates the end of the acute phase and the formation of immunity to the virus. IgG antibodies to HAV also appear after the vaccination against hepatitis A and persist throughout life, providing immunity. The presence of IgG antibodies in blood indicates transferred past infection or vaccination against the virus.