Various Causative organisms in viral hepatitis

The differing features of the common forms of viral hepatitis are summarized below: In HAV the damage is due to the cirus itself, but in HBV infection it is due to an immunological reaction to the virus.

Hepatitis A:

This is the commonest type of viral hepatitis and causes 20-40 percent of clinically apparent hepatitis. It occurs worldwide, often in epidemics.

The disease is commonly seen in the autumn and effects children and young adults. Spread of infection is mainly by the faecal oral route and arises from the ingestion of contaminated food or water.

Overcrowding and poor sanitation facilitate spread. There is no carrier state. HAV is a picornavirus. It has a single serotype as only one epitope is immunodominant.

It is excreted in the faces of infected persons for about 2 weeks before the onset of the illness and for upto 7 days after.

The disease is maximally infectious just before the onset of jaundice. HAV particles can be demonstrated in the faeces by electron microscopy.

Hepatitis B:
The virus HBV is present worldwide and has infected more the 2000 million people. There are an estimated 350 million carriers. The UK and the USA have a low prevalence but it rises to 10-15 percent in parts of Africa, the Middle and the Far East.

Spread of this virus is by intravenous route, eg, transfusion of infective blood or blood products, by contaminated needles used by drug addicts, tattooists or acupuncturists or by close personal contact, eg, sexual intercourse, particularly in male homosexuals.

The virus can be found in semen and saliva. Vertical transmission from mother to child during parturition or soon after birth is the most important means of transmission worldwide.

The role of insect vectors is controversial, there is no evidence that HBV replicates in these insects but the virus has been detected in mosquitoes and bed bugs.

Hepatitis B Virus:
Under electron microscopy a number of particles are seen. The whole virus is the Dane particle, which consists of an inner core formed by the liver cell nucleus and an outer surface coat produced by multiplication in the cytoplasm.

The inner core contains double stranded DNA, DNA polymerase, the core antigen and the e antigen. Small spheres and tubules of excess surface antigen protein are also produced. The virus only replicates in the liver.

The core antigen enters and replicates in the nucleus and eventually becomes integrated with the host nuclear DNA. The host DNA polymerase then transcribes for the virus. This may be an important link in the development of hepatocellular carcinoma.

Hepatitis B mutants:
Mutations are being increasingly described in the various reading frames of the HBV genome. These mutants can emerge in chronic HBV carriers or can be acquired by infection.

These variants of the HBV genome have also been found in patients with fulminant and fatal hepatitis who have HBsAg and anti-HBe rather than the e antigen itself.

Hepatitis C:
HCV was identified in 1988 and was responsible for 70-90% of post transfusion hepatitis in all countries where blood was tested for HBV markers.

Since the screening of HCV in donor blood was introduced, this incidence has felled to 4%. It is transmitted by blood and blood products and it is postulated that 76% of hemophiliacs in the UK may have been infected.

The incidence in intravenous drug abusers is very high. A high prevalence amongst homosexual men suggests sexual transmission and it may be transmitted from mother to child. Other routes of community acquired infection, eg close contact are unlikely.

In many cases the exact mode of transmission is unknown. HCV is a single stranded RNA virus arranged into structural and non structural regions. There are six subtypes based on differences in the nonstructural region.

Only types I, II and III and seen in Europe and type IV occurs in the Far East. Immunogenic peptides have been derived from these regions for use in HCV assays and are becoming increasingly sensitive. The concentration of viral antigens in the blood is very low.

| Various complications in viral hepatatis | Different types of viral hepatitis | Treatment process of viral hepatitis | What are the various Causative organisms in viral hepatitis | How to treat & prevent viral hepatitis | What is Prognosis in viral hepatitis | Conceived your First Baby with Hepatitis C in your Blood? | Got Diagnosed for Hepatitis C Infection? | The Difficult Task of Diagnosing Hepatitis C in Aged People | How to deal with Emotionally Disturbed Hepatitis C Infected Persons | How to Handle the Undeterred Hepatitis C Infection Spread | Know the Multiple Entry Routes of Hepatitis C Infection | How to Trap and Fix Eluding Hepatitis C Symptoms in a Person | Correlativity between Hepatitis C and HIV Infection | Varied Treatment Options for Your Hepatitis C Infection | How Young Children Play Safe with Hepatitis C Viral Infection |

What are the various Causative organisms in viral hepatitis?