Viruses
Hepatitis
A virus (HAV)
This is described in Chapter 52.
Hepatitis
B virus (HBV)
This may follow blood transfusion, plasma infusion and, rarely, the
administration of sera, infection resembling infective hepatitis except that
the incubation period is about 12 weeks. Transmission by plasma has been reduced
by avoiding the pooling of plasma from a large number of donors. Transmission
by syringes is prevented if all syringes are disposable. It occurs amongst those
who are drug addicts and possibly after tattooing or ear piercing. There is an
extremely high rate among certain homosexual communities. In certain centres
more than 50 per cent of male homosexual patients have antibody indicating
exposure and about 5 per cent have active disease. In Athens, a group of
prostitutes was found to have a rate 20 times that of married pregnant women,
possibly due to more frequent coitus near the period or to other sexually
transmitted diseases, producing bleeding that transmits the infection.
Infection
with hepatitis B virus is associated with the appearance in the blood of one or
more antigens, viz, hepatitis B surface antigen (HBsAg), hepatitis Be
antigen (HBeAg), the Dane particle (probably the complete virus) and DNA
polymerase activity. Under electron microscopy, particles can be seen in the
sera of these patients and are associated with the virus. These particles are
antigenic. Such patients usually suffer the severest form of hepatitis. The
antigen is the scourge of renal dialysis and transplantation units, and hospital
staff must avoid contact with blood from such patients.
A
genetically engineered vaccine is now available (Engenix
Good antibody levels usually persist for about 5 years and a
booster is recommended at this time. It is important that the injection is given
intramuscularly in the deltoid as this produces a higher response rate than the
buttock. All surgeons are strenuously recommended to have a course of this
vaccine.
Hepatitis
nonA nonB is a variant, with an incubation period similar to HBV but with milder
clinical features. Several causative agents have been described, one of which is
hepatitis C. Detection of antibodies to hepatitis C indicates exposure to the
disease and the presence of viral nibonucleic acid (RNA) in the blood indicates
chronic infection. There is a number of serotypes with varying responses to
therapy with a combination of interferon and ribavinin. Sadly, a large number of
patients relapses after treatment and the development of new and more effective
antiviral agents is awaited.