hepatitis B virus
- can occur via a number of routes - percutaneous (needlestick, IVDU, tatooing, or body piercing), parenteral (transfusions), transdermal if broken skin, mucosal (especially anal intercourse), or vertical transmission during perinatal period.
- it seems vertical transmission from mother to baby can be prevented by giving the mother tenofovir, an antiviral agent, in the 3rd trimester through to 8 weeks post-partum.
- following exposure, acute hepatitis B infection has an incubation period of 6-12 weeks
- adults commonly develop symptoms of jaundice (icterus), anorexia, nausea, RUQ discomfort and fatigue, but fortunately, over 95% will spontaneously clear the virus
- only 30% of children will spontaneously clear the virus
- perinatal acquisition is commonly asymptomatic but only 5% will clear the virus
- 1% may develop acute liver failure and develop hepatic encephalopathy - these patients should be referred to a transplant unit
- Rx is mainly supportive
chronic hepatitis B
- affects some 160,000 people in Australia - mainly non-Westerners (presumably due to lack of access to vaccination prior to migration) but including Mediterranean Europe.
- shortens life span of 45% of infected men and 15% of infected women due to development of cirrhosis or hepatocellular carcinoma
phases of chronic hepatitis B
- phase 1 - immune tolerance
- usually lasts for 20-40 years
- high levels of viral replication, persistently normal ALT
- HBeAg but no antibodies to this
- minimal damage, thus no liver biopsy or antiviral Rx required
- advise periodic LFT monitoring watching for rise in ALT which signals phase 2
- phase 2 - immune clearance
- more vigorous immune response resulting in liver damage with intermittently raised ALT and elevated viral DNA
- repeated episodes of inflammation leads to fibrosis, and duration and severity of this phase determines degree of long term liver damage
- 30-40% of patients emerge with established cirrhosis
- 5-10% of patients each year will spontaneously lose HBeAg and develop antibodies to HBeAg - “seroconversion” which results in reduced viral replication.
- median age for seroconversion is 30-32 years
- if ALT is persistently raised, refer to hepaologist for possible biopsy and Rx.
- phase 3 - immune control
- immune response suppresses viral replication to low or undetectable levels
- inflammation reduces and ALT normalises
- once seroconversion has occurred, patients may remain in this phase indefinitely.
- most do not require antiviral Rx in this phase, but many will have established cirrhosis and require careful assessment
- phase 4 - immune escape
- virus mutates and loses it's ability to make the HBeAg allowing it to replicate, resulting in recurrence of active liver disease and progressive fibrosis
- persistely elevated or fluctuating ALT levels with HBeAg negative status, but elevated viral DNA
- usually patients are older than 40 years
- given the high risk of cirrhosis - 8-10% per year, consider long term Rx to suppress viral replication
hbv.txt · Last modified: 2014/03/19 00:07 by 127.0.0.1