Communicable Diseases
Hepatitis B
Hepatitis B is a global problem characterized by its preponderence to cause cirrhois, liver failure and hepatocarcinoma, its long duration of illness, and production of carriers. It is 50–100 times more infectious than HIV, and an important occupational hazard for health workers.
Agent
The hepatitis B virus (HBV) is one of the family Hepadnaviridae and genus Orthohepadna, a DNA virus with a reverse transcriptase enzyme. It survives in external environment for some days; destroyed by NaOCl and autoclaving.
Antigens
- The surface antigen (HBsAg) which is the marker of infection.
- The core/'insoluble' antigen (HBcAg) present in the capsid of the virus; it is only expressed in the surface of liver cells after infection, and never found in blood.
- The 'soluble' antigen (HBeAg), a component of nucleocapsid, is secreted in blood and is an indicator of ongoing virus replication.
Host
Any age and sex is susceptible; neonates may acquire infection by placental transmission and they are very prone to become carriers. Recovery from disease gives life long immunity.
High risk group
- Medical personnel
- Laboratory workers
- Homosexuals (anal sex causes more epithelial damage than vaginal sex)
- IV drug users
- Infants of infected mothers (becomes a chronic carrier)
- Patients of repeated blood transfusion.
Incubation Period
Communicable period is 1 month before onset of jaundice appearance of antiHBs in blood.
There are 4 main modes of transmission:
- Blood, blood products, contaminated syringes and needles, skin pricks,
- Sex (specially anal sex)
- Transplacental
- By physical contact from child to child (throuch cuts, abrasions and grazes).
Clinical course
Incubation period 50–180 days, extremely variable. After an exposure, two-thirds of cases develop an acute hepatitis, showing a fl u like syndrome and jaundice, and the rest one third only have a subclinical infection.
Prognosis
- About 90–95% patients (who have good cell mediated immunity) recover with resolution of liver in 1–2 months and eliminate the virus entirely from the body in 6 months.
- 0.5% of patients with hypersensitivity (and coinfection with hepatitis D) develop fulminant hepatitis, often fatal.
- 5–10% of patients with limited cell mediated immunity progress to chronic hepatitis B (HBsAg persisting in blood for more than 6 months).
Carriers
People with deficient cell mediated immunity usually becomes a carrier of HBV. Simple carriers bear either HBsAg or HBeAg in their blood. Super carriers bear both in blood.
Complications
Hepatic complications. Chronic hepatitis, hepatocarcinoma, fulminant hepatitis Extrahepatic. Serum sickness like reaction, arthralgia, acute glomerulonephritis, myalgia (due to immune complex deposition).
Labs
Serology gives the definitive diagnosis in following diagram.
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