Hepatitis B virus is a hepadnavirus (hepa from
hepatotrophic and dna because it is a DNA virus) and it has a circular genome
composed of partially double-stranded DNA. The viruses replicate through an RNA
intermediate form by reverse transcription, and in this respect they are
similar to retroviruses (Locamini, 2004). Although replication takes place in
the liver, the virus spreads to the blood where virus-specific proteins and
their corresponding antibodies are found in infected people.
Originally known as “serum hepatitis”, the
disease has caused epidemics in some parts of Africa and Asia, and it is endemic
in China (Williams, 2006).
Infection with hepatitis B virus is a serious global public health problem and remains a major cause of morbidity and mortality in the continent of Africa and Asia (Weinbaum et al., 2008 and Andre, 2004).
Infection with hepatitis B virus is a serious global public health problem and remains a major cause of morbidity and mortality in the continent of Africa and Asia (Weinbaum et al., 2008 and Andre, 2004).
The prevalence of HBV infection and
the predominant mode of transmission vary greatly depending on the geographical
regions and epidemiological factors (WHO, 2001).
More
than 2 billion people have been infected with hepatitis B virus (WHO 2009) and
this includes 350 million chronic carriers of the virus. An estimated 1-2
million deaths due to hepatitis B virus have been recorded annually (Maddrey,
2000).
Transmission of hepatitis B virus
results from exposure to infectious blood or body fluids such as semen and
vaginal fluids, while viral DNA has been detected in the saliva, tears and
urine of chronic carriers with high titre DNA in serum. Perinatal infection is
a major route of infection in endemic (mainly developing) countries (Coopstead,
2010).
Other risk factors for developing
hepatitis include working in a health care setting, transfusion, and dialysis,
acupuncture, extended overseas travel and residence in an institution
(Sleisenger et al., 2006, Kidd-Ljunggren et al., 2006 and WHO
2009).
However, hepatitis B virus cannot be
spread by casual contact such as holding hands, sharing eating utensils or
drinking glasses, breast feeding, kissing, hugging, coughing or sneezing. The
acute illness causes liver inflammation, vomiting, jaundice and rarely death. Chronic
hepatitis B may eventually cause cirrhosis and liver cancer – a fatal disease with
very poor response to chemotherapy (Chang, 2007). HBV infection is the most
common cause of liver disease The infection is preventable by vaccination and
routine screening of all pregnant women for HBV infection (Maddrey, 2000).