Hepatitis B

The hepatitis B is a viral infection of the Foie by the virus of hepatitis B.

Virus of hepatitis B

The virus of hepatitis B (VHB) is a virus with DNA pertaining to the family of the Hepadnaviridae. The principal symptoms are a Ictère (jaundice), a fever and a prolonged tiredness. The virus is very resistant, it is strongly contagious, 100 times more than that of the AIDS. According to the the World Health Organization there would be 350 million carriers of the virus in the world. In the blood of a patient in active phase of viral synthesis, one can observe 3 types of structured:

of the spheres of 20nm of diameter,
of the tubules of 20nm of diameter and 200 with 700nm length which is a stacking of the spheres,
“particles of Dane” of 42nm of diameter, corresponding to the whole viral particles, made up of a core (Nucléocapside containing a DNA double bit associated with ADNpol) as well as envelope.

The particles of Dane represent the complete virus whereas the spheres and the tubules only correspond to the envelope of this last.

Duration of incubation

The period of Incubation varies from 45 to 180 days, but the average is from 60 to 90 days, the duration being able to increase or decrease according to the gravity of the infection.

Modes of contamination

blood transmission by transfusions or of blood products (rare since the exclusion of the AgHBs donors + and anti-HBc ac +).
Iatrogenic transmission by material not sterilized (surgery, invasive exploration, dental acupuncture, mésothérapie, care); The evolution of the rules of sterilization and the generalization of the use of material of single use make it possible to avoid it.
accidental puncture
transmission by intravenous Drug-addiction , tattooing, Piercing.
sexual transmission, by interindividual heterosexual, homosexual or not-sexual contact. (The Préservatif S are good means of protection here).
vertical transmission in period néonatale; the tracking of Ag HBs during the pregnancy allows the serovaccination of the newborn (in the first 48 hours).

Prevalence

One estimates into 2007 that 2 billion people approximately is annually infected by the VHB, primarily in tropical zone. More than 360.000.000 among them will be infected in a chronic way. 600.000 personnens die about it annually.

Varied levels of séroprévalence of the VHB are explained by the socio-economic context and of vaccination: it allows weak prevalence, for example in the Island of the Meeting (or only 0,7% of the population are touched), whereas in Black Africa it often exceeds 15% (ex: with Madagascar, the prevalence is of 16%, because of frequent transmission mother-child and of the weak use of the condom, which supports a frequent sexual transmission).

Evolution

The virus of hepatitis B cures spontaneously in 90 % of the cases. In 1 % of the cases occurs a fulminant hepatitis. 10 % of the patients see their hepatitis B evolving/moving in chronic form (90% in the infants). These chronic forms can cause lesions of Cirrhose, leading to the cancer hépatocellulaire (15% to 25% of the chronic carriers die of the complications by cirrhosis or cancer of the liver).

Until the end of the 20th century, the rate of cure was of 30 % (to be checked, META reference) with very heavy treatments (Interféron). This disease annually caused more than one million premature deaths.

Certain patients carrying the virus do not present a hepatic attack; they are called healthy carriers.

Treatment

curative Treatment:
Its objective is to prevent the evolution towards the cirrhosis and cancer, at the patient having chronic hepatitis B with viral replication and histological hepatic lesions. Its evaluation rests on biological criteria (Ag HBe, viral DNA, ac antiHBe) and histologiques
The antiviral treatment of first intention is the peginterféron esparto-2a during 24 to 48 weeks, which with the advantage of only one weekly injection instead of 3 for the interféron esparto . The profile of undesirable effects is similar for these two products. Remainder the effectiveness of the peginterféron esparto-2a is comparable with that of the interféron esparto which involves a prolonged disappearance of AgHBe in 20 to 40% of the cas.
The other antiviral ones are used in second intention: to adéfovir dipivoxil and Lamivudine when the head end is insufficiently effective or because of its undesirable effects. The to entécavir is currently used in third intention. The other antiviral ones are in the course of evaluation: the emtricitabine , the to ténofovir , the telbivudine , the clévudine .
In the event of décompensée hepatic attack, the hepatic Transplantation is the only effective cure in a durable way.

Treatment préventif'
Vaccination: The principal complication is the Cirrhose liver accompanied by a risk of Carcinome hépatocellulaire (in more than one case for 1000), this is why WHO recommends since 1998une massive vaccination against the HVB (to vaccinate all the infants and teenagers against the VHB makes it possible to reduce the rate of the carriers from approximately 90% in 25 years).
a first vaccine human was obtained by genetic Engineering starting from animal cells, by the team of Pierre Tiollais in 1985.
La balances benefit-risks of the vaccines of hepatitis B is considered favorable at the people not immunized and exposed at the risk of hepatitis B.
Chez the newborn of positive mother Ag Hbs, specific Immunoglobulins and a vaccination with the birth make it possible to reduce the mother-child transmission risk of 92%.

See too

Internal bond

External bond

S.O.S Hepatitises

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