- The Hepatitis B virus is a single stranded DNA virus
- Consists of 42 nm Dane particle (HbsAg) and 22 nm core (HbcAg)
- HbsAg - Hepatitis B surface antigen = Australia antigen
- HbcAg - Hepatitis B core antigen
- HbsAb - Hepatitis B surface antibody
- HbeAg - Hepatitis B 'e' antigen
- In UK prevalence of HbsAg positivity is 1-2%
- Seen particularly in drug addicts, homosexuals, dialysis patients and occasionally medical staff
- In Asia, Middle East and South America prevalence is between 20-30%
- Transmitted by vertical transmission, inoculation, oral and sexual contact
- Incubation period between 6 weeks and 6 months
- Period
of infectivity is from 6 weeks before onset of symptoms and possibly indefinitely after
- 10% of infected patients become chronic carriers
- Risk of chronic infection varies with age at which infection is acquired
- Less than one year = 90%
- 1-5 years = 30%
- Greater than 5 years and adult = 2%
Clinical pictures
- Acute hepatitis with clinical recovery
- Acute fulminating hepatitis leading to death
- Chronic active hepatitis with risk of cirrhosis and hepatocellular carcinoma
Serological results
HbsAg positive
- The first indicator of infection and seen throughout course of disease
- Persistence is marker of failure to clear infection
HbsAb positive
- Marker of protection due to either previous infection of immunisation
HbeAg positive
- Closely associated with infectivity of patient
Prevention of infection
- Avoid contact with virus
- Care with needles, body fluids etc
- Hyperimmune anti-Hepatitis B IgG
- Useful after needle stick injury from high risk patient
- Ideally given with 24 - 48 hours after exposure
- Repeated at one month
- Immunisation
- All paramedical staff should be immunised
- Energix B given and repeated at one and 6 months
- HbsAb levels >1000 u/l = adequate response
- Confers protection for up to 5 years
Treatment
- Two modes of treatment
- Immunomodulation = interferon
- Viral suppression = nucleoside analogues
Bibliography
Fry D E. Hepatitis: risks for the surgeon. Am Surg 2000; 66: 178-183.
Lai C L, Ratziu V, Yeun M-F, Poynard T. Viral Hepatitis B. Lancet 2003; 362: 2089-2094.
Welsh K, Alexander G J. Update on chronic viral hepatitis. Postgrad Med J
2001; 77: 498-505. |