Hepatitis B virus ( HBV ) is the most common human hepatitis virus in Singapore. HBV infection and its chronic sequelae are major world-wide health problems. There are approximately 300 million chronic HBV carriers in the world, of whom 75% are found in the Asia Pacific region. It is estimated that between 25 to 50 percent of these carriers can expect to die prematurely, either as a result of chronic liver inflammation and liver failure (cirrhosis) or the development of liver cancer.

6% of the Singapore population are hepatitis B carriers. Most hepatitis B infection is acquired during birth and in early childhood. These infections are generally asymptomatic. These carriers remain well for long periods and are discovered incidentally during blood donation, health screening or screening prior to vaccination. While the number of acute hepatitis B has decreased over the years, largely as a consequence of universal vaccination and screening of blood donors, doctors still have to deal with problems of chronic liver inflammation, liver cirrhosis and cancer.

How is hepatitis B transmitted, and who are at a higher risk of acquiring the infection?

• Transmitted through body secretions like blood, semen, saliva.
  
• Babies of hepatitis B carrier mothers are infected at the time of birth or soon after birth.
• Transmission in childhood can occur through shared utensils like toothbrushes and razors.
• Hepatitis B infections can be acquired through blood transfusions if the blood donor is not properly screened for the infection.
• HBV infections can also be acquired through acupuncture, tattooing, ear piercing, manicures and dental treatment if non-sterile instruments are used.
• Healthcare workers like doctors, dentists and nurses are at risk of finger-prick injuries which also transmit HBV infection.
• Unprotected sex promotes HBV transmission. Therefore, individuals who indulge in a promiscuous lifestyle like commerical sex-workers and homosexuals are at a higher risk of HBV infection.

Hepatitis B virus in babies and adults

A baby who acquires the hepatitis B infection manifests a different course of illness from one who is infected in adulthood. Generally, an infection contracted at birth (from mother-to-child), does not manifest in any symptoms. Following such an infection the baby has a 90% chance of becoming a hepatitis B carrier, because they are unable to eliminate the virus from their bodies.

On the other hand, an individual who acquires the infection as an adult displays symptoms of "acute liver inflammation" (acute hepatitis B). Of these patients, 1% develop a very serious clinical course known as fulminant viral hepatitis B. These patients deteriorate very rapidly during the clinical course of the illness and may go into liver failure or even die. However, newer modalities of treatment like liver transplantation exist.