Hepatitis A, (formerly known as infectious hepatitis) is a viral hepatitis, an acute infectious disease of the liver caused by hepatitis A, transmitted most often by oral-faecal food or water contaminated. Each year approximately 10 million people are infected with the virus in the world. The time lag between infection and the onset of symptoms (incubation period), is two to six weeks and the average incubation period is 28 days.
In developing countries, and in areas where sanitary conditions are poor, the incidence of infection by the virus is close to 100% and the disease is usually contracted in infancy. The infection by the hepatitis A virus does not cause any clinical signs or symptoms detected in more than 90% of children and the fact that the infection confers lifelong immunity, the disease has no particular importance for Aboriginal population. In Europe, the USA and other industrialized countries, against the infection is contracted mainly by young adults not immunized, most of whom are infected with the virus during travel in countries with a high incidence of the disease.
Hepatitis A does not pose a risk of progression to a chronic and does not cause chronic liver damage. After infection, the immune system produces antibodies against hepatitis A which give the patient an immunity against future infections. The disease can be prevented by vaccination and the vaccine against hepatitis A has been proven effective in controlling outbreaks of epidemics in the world.
The hepatitis A virus (HAV) is a picornavirus. It is an RNA virus without envelope and surrounded in a capsid protein. There is only one serotype of the virus.
After being ingested, HAV invades the bloodstream through the epithelium of the pharynx or intestine. The blood carries the virus to its target, the liver where it multiplies in the hepatocyte cells and Kupffer (ie, liver macrophages). There is apparently no cytotoxicity direct virus and reaching the liver is a consequence of the immune response. The virus is excreted in bile, and excreted in the stool. The HAV is excreted in large quantities for about 11 days before the onset of symptoms or IgM antibodies anti-HAV in the blood. The incubation period is 15 to 50 days, and the mortality rate is less than 0.5%.
The virus spreads through oral-faecal and infections often occur in circumstances of poor sanitation and overcrowding. Hepatitis A can be transmitted through parenteral, but very rarely by blood and blood products. The outbreaks of food poisoning are not uncommon, and the ingestion of shellfish which have remained in polluted water is associated with a high risk of infection.
About 40% of acute viral hepatitis are due to HAV. The infected people are contagious before the onset of symptoms, roughly 10 days after infection. The virus is resistant to detergents, acidic (pH 1), solvents (for example, ether, chloroform), the drying and heat until 60oC. It can survive for months in freshwater and saltwater The outbreaks are typically linked to a common source (for example, drinking water, a restaurant ...). The infection is common among children in developing countries, reaching an incidence of 100%, but after infection, immunity persists throughout life. The HAV may be inactivated by the chlorine treatment] (drinking water), formaldehyde (0.35%, 37oC, 72 hours), peracetic acid (2%, for 4 hours), beta-propiolactone ( to 0.25%, for 1 hour), and ultraviolet (2 μ W/cm2/min).
Early symptoms of hepatitis A can be confused with flu, but some patients, especially children, have no symptoms at all. The symptoms usually appear 2 to 6 weeks, (incubation period), after initial infection.
The symptoms may recur for 6 to 9 months after the beginning of infection are as follows:
* Loss of appetite
* A weight loss
* Pain (s) abdominal (s)
* Diarrhea or constipation
* Jaundice, a yellowing of the skin or whites of eyes
* Pain in the upper right quadrant of the abdomen
Although the virus is excreted in the stool only at the end of the incubation period, the precise diagnosis can be made before that date by the detection in the blood IgM antibodies specific virus of hepatitis A. The IgM antibodies are present in the blood only after the acute infection by the virus of hepatitis A. It is detectable one to two weeks after the initial infection and persists until 14 weeks. The presence of IgG antibodies in the blood means that the acute phase of illness is over and that the person is protected by a new infection. The IgG antibodies against the HAV are also found in the blood after vaccination and testing of immunity against the virus are based on the detection of such antibodies.
During the acute phase of infection, liver enzymes whose Alanine amino transferase (ALT) are present in the blood at levels much higher than normal. The enzymes from the liver cells that were damaged by the virus. The hepatitis A virus is present in the blood (viremia), and feces of infected persons up to two weeks before the onset of clinical disease.
Complications are rare but in one case in 1000, the patient can develop fulminant hepatitis.
There is no specific treatment for hepatitis A. It is advisable for patients to rest, avoid fatty foods and alcohol (which may be poorly tolerated for a few months during the phase of convalescence and cause minor relapses), to have a balanced diet, and hydrate well. Approximately 15% of patients who were diagnosed with hepatitis A have one or more symptoms of relapse during a period of 24 months after contracting the disease.
The Centers for Disease Control and Prevention of USA (CDC) reported in 1991 a low mortality rate for hepatitis A set at 4 deaths per 1000 cases for the general population, but a higher rate 17.5 per 1000, for people aged 50 and older. Death usually occurs when the patient contracted hepatitis A while already suffering from another form of hepatitis, such as Hepatitis B, Hepatitis C or AIDS.
Hepatitis A can be prevented by the vaccine against hepatitis A, good conditions of hygiene and sanitation.
The vaccines against hepatitis A confer protection against the virus. The vaccines contain viruses hepatitis A inactivated induces an active immunity against future infection.
The HAV is found in feces of infected patients and people at high risk are travelers staying in developing countries where there is an incidence rate higher, and those who have sexual contact with people infected or are using drugs intravenously. The CDC estimates that USA, there were 30 000 cases in 1997, and approximately 127 000 new cases each year from 1980 to 1999.
Outbreaks of HAV still occur because of improper hand hygiene among those infected, some restaurant employees showing symptoms and neglecting to wash their hands after their passage to the toilet.
The largest outbreak of hepatitis A in America has hit at least 640 people (killing four) in the north-east of Ohio and south-west of the PA at the end of 2003. The epidemic has been attributed to contaminated green onions at a restaurant in Monaca, Pennsylvania. In 1988, 300 000 people in Shanghai, China were infected with HAV after eating clams from a river contaminated.
Read also Hepatitis B, Hepatitis C