Acute hepatitis may occur as part of the clinical course of a number of viral infections, including Human Cytomegalovirus, Epstein-Barr virus, Herpes Simplex Virus, Yellow Fever Virus and Rubella. But the term "hepatitis virus" is usually used to describe infections caused by agents whose primary tissue tropism is the liver. To date, at least five hepatitis viruses have been recognised and these have been named, hepatitis A, B, C, D and E.
ENTERICALLY TRANSMITTED HEPATITIS: A and E
Incubation period 3-5 weeks (mean 28 days)
World-wide distribution; endemic in most countries. The incidence in first world countries is declining. There is an especially high incidence in developing countries and rural areas, where 80-90% of people are infected by the age of 5 years. The implication for South Africa is that most people, especially from rural areas, are seropositive, and donated blood/plasma contains sufficient levels of antibodies for use as passive immunity.
Transmission: Faecal-oral route
Infected food handlers
Virus cannot be cultured in vitro from clinical material; diagnosis depends on:
Incubation period: 45 days [2-9 weeks]
10 % develop fulminant hepatitis (more common in pregnant women). Mortality rate is high (20-40 %). Chronic hepatitis may develop in organ transplant patients and HIV-infected individuals and lead to cirrhosis.
Acute hepatitis E is similar to hepatitis A; virus replicates in the gut initially, before invading the liver and virus is shed in the stool prior to the onset of symptoms. Viraemia is transient. A large inoculum of virus is needed to establish infection. Chronic hepatitis E infection seems similar to chronic hepatitis C infections, but much about the pathogenesis is unknown.
Prevalence of infection appears to be low in first world countries. Large outbreaks have been described in India, Mexico and North Africa where the source of infection is usually gross faecal contamination of drinking water supplies, which is the main source of infection.
Outbreaks of hepatitis E have been confirmed in South Africa, but the prevalence of infection is unknown, as there are no routine laboratory tests yet available.
No routine laboratory tests are available as yet in South Africa. Virus cannot be cultured in vitro.
PARENTERALLY TRANSMITTED HEPATITIS B, C and D
Incubation period is long: 30-180 days, average 75 days
Infection is parenterally transmitted. The virus replicates in the liver and virus particles, as well as excess viral surface protein, are shed in large amounts into the blood. Viraemia is prolonged and the blood of infected individuals is highly infectious. The host immune response to the virus is responsible for hepatocellular damage.
Prevalence of disease in Africa
Hepatitis B is parenterally transmitted
Perinatal transmission from a carrier mother to her baby
Blood transfusions, serum products
All these vaccines are equally safe and effective. Three doses induce protective levels of antibodies in 95% of vaccine recipients.
Treatment of Chronic Hepatitis B infection
Two classes of drugs are used to treat chronic HBV infection
Note: * also used to treat HIV
1) surface antigen (sAg) surface (envelope) protein of the dane particle
2) e antigen (eAg) secreted protein; shed in small amounts into blood
3) core antigen (cAg) core protein
1) Surface antibody (sAb, antiHBs)) becomes detectable late in convalescence following resolution of infection, remains detectable for life; not found in chronic carriers; indicates immunity
2) e antibody (eAb, antiHBe) becomes detectable as viral replication falls
3) Core IgM rises early in infection
4) Core IgG Rises early
HBV viral load:
Hepatitis B serology
(a) Acute, self limiting infection
(b) Chronic carrier state
The major cause of parenterally transmitted non A non B hepatitis. It eluded identification for many years because the virus could not be cultured. In 1989, the viral genome was cloned and sequenced from the serum of an infected chimpanzee. Much of the knowledge that we have today is based on analysis of its genome sequence
Genome has a high mutation rate
The incubation period is 15-150 days. Most common presenting symptoms are fatigue and jaundice, but 60-70% of cases are asymptomatic. It is the cause of 15-20 % of acute hepatitis in the developed world. Of note, 80% of newly infected individuals develop chronic infection..
Complications of chronic infection:
Approximately 170 million people are infected world wide. The prevalence is high in parts of Africa, the Eastern Mediterranean and South East Asia.
Transmission - similar to HBV
Intravenous drug abusers
Treatment of Chronic infection: Interferon a in combination with Ribavirin results in clearance of infection in up to 40% of cases. Pegylated interferon a is interferon that has had polyethylene glycol attached to it. This increases the half life, which leads to fewer side effects due to a lower dose being used.
There is no vaccine available
Hepatitis D Virus (delta agent)
In 1977 an novel protein was discovered in the serum of some patients who were infected with Hepatitis B. It was named the delta antigen. Subsequent investigation showed that the protein was encoded by a new virus, now called the hepatitis D virus (HDV).
Two forms of infection can occur - co-infection, where the person becomes infected with HDV and HBV at the same time, and superinfection, where the person becomes infected with HDV after the initial HBV infection. HDV leads to increased severity of liver disease in Hepatitis B carriers, and the acute infection has an incubation period of about 35 days. Fulminant hepatitis is ten times more common when a patient is co-infected with both viruses (HBV and HDV) simultaneously. With only HBV, 20-30% go on to develop cirrhosis, while that figure rises to 70-80% with co-infection and superinfection.
First identified in intra-venous drug abusers in Italy. Has since been shown to be present in other parts of Europe as well as parts of North and South America. The incidence in South Africa is unknown.
Treatment and prevention
محتويات مواقع أعضاء هيئة التدريس بما فيها من نصوص وملفات وصور وأبحاث وأية مواد أخرى هي مسئولية عضو هيئة التدريس بالكامل بصفته صاحب الموقع وبما له من صلاحية مطلقة في الإضافة والحذف، وتخلي الجامعة مسئوليتها عن محتويات تلك المواقع.
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