Bugs – Hepatitis B
Hepatitis B is one of the range of viral diseases which affect the liver and can cause long term morbidity as well as mortality in certain patients. Estimates suggest that over two billion people throughout the world are currently infected or have been at some stage during their life.
Mode of Infection
Contact with body fluids such as through contaminated needle-stick injury or via perinatal contact from mother to child account for the main risk of transmission. The virus has been isolated from semen, vaginal fluid, tears and saliva. Even though the virus has been isolated from various blood-sucking arthropods (eg mosquitoes & bedbugs) there is no evidence of multiplication of the virus in these insects. Direct transmission can occur and care should especially be taken when squashing any of these insects in a high-risk part of the world.
Generally most patients who become infected show an incubation period of between two to six months. In the prodromal stage patients usually develop fever, a flu-like illness, joint aches and a loss of appetite. Headache can also be a pronounced symptom and occasionally patients show a skin rash. Jaundice develops at this stage accompanied by dark urine and a pale stool. In the majority of cases recovery starts after about three to four weeks. The itchy skin reaction and constitutional changes with Hepatitis B may be significantly less than those experienced with Hepatitis A.
About 2% to 10% of adults infected by Hepatitis B progress to become chronic carriers with Hepatitis B surface antigen (HBsAg) persisting in their serum for longer than six months. These patients have a long-term risk of developing some of the more significant complications from this disease including Cirrhosis and Liver Cancer. Children have a much higher risk of becoming carriers and in those infected at birth this level rises to a staggering 90%. Most carriers are, as excepted, asymptomatic though some do present with non-specific lethargy and malaise.
It has been estimated that Hepatitis B is about 100 time more infective than the human immunodeficiency virus (HIV). The majority of cases will resolve over a few months though a number of those infected may develop into long term carriers who are capable of transmitting the disease to others.
Numerous attempts have been made to treat this viral disease with agents such as Interferon and Aednine arabinoside. Trials are still on-going and a number of other agents are being tested but in the majority of the world, where this disease is most prevalent, these agents are unavailable. Generally supportive therapy is used as the sole line of therapy.
The World Health Organisation has set a target of 2010 for the eradication of the disease throughout the world. Whether or not this is achievable depends greatly on the motivation of individual countries to instigate a control programme with active vaccination. Until the disease has been eradicated tough, travellers should take care not to come in contact with bodily fluids as described above during their travels see Sexually Transmitted Diseases. Vaccination can be considered as second-line defence.
In South Africa 2 choices of vaccine are available, both options require an initial vaccine with two booster doses administered over a six month period. It is estimated that between 80% to 90% of adults seroconvert and are provided with long term protection.