HBV

Group: Group VII (dsDNA-RT)

Family: Hepadnaviridae

Genus: Orthohepadnavirus

Species: Hepatitis B virus

• Genome is partially double-stranded DNA that forms a covalently closed circle with 5′ end of the full length minus strand which is linked to the viral DNA polymerase.

• Circular, non-segmented and approximately 3.2 kilobase (kb) in size.

• The genome is 3020–3320 nucleotides long (for the full length strand) and 1700–2800 nucleotides long (for the short length strand).

• Compact organization, with four overlapping reading frames running in one direction and no non-coding regions.

Fig: Genetic organization of the hepatitis B virus genome. Four open reading frames encoding seven peptides are indicated by large arrows

• Hepatitis B prevalence is highest in sub-Saharan Africa and East Asia, where between 5–10% of the adult population is chronically infected.

• Globally, 240 million people infected with hepatitis B and 786,000 people die every year due to complications of hepatitis B.

• In 2013, there were an estimated 19,764 new hepatitis B virus infection in the United States with an estimated 700,000 to 1.4 million persons having chronic hepatitis B virus infection.

- Only 30% to 50% of adults develop significant symptoms during acute infection.

- The incubation period of the hepatitis B virus is 75 days on average, but can vary from 30 to 180 days.

• Fever, a flu-like illness.

• Fatigue.

• Dark urine.

• Loss of appetite.

• Nause, Vomiting.

• Joint pain.

• Clay-colored bowel movements.

• Jaundice (yellowing of the skin and eyes).

• Pain in the upper right abdomen (due to the inflamed liver).

• People with chronic Hepatitis B develop serious liver conditions, such as cirrhosis (scarring of the liver) or liver cancer.

• Transmitted through blood and infected bodily fluids as well as through saliva, menstrual, vaginal, and seminal fluids.

• Transmit through direct blood-to-blood contact, unprotected sex, use of unsterile needles, and from an infected woman to her newborn during the delivery process.

• Infection can occur during medical, surgical and dental procedures, tattooing, or through the use of razors and similar objects that are contaminated with infected blood.

• Rarely, hepatitis B can be transmitted through transfused blood products, donated livers and other organs.

• Hepatitis B is not spread through food, water, or by casual contact

TREATMENT

• The goal of treatment for chronic hepatitis B is to suppress HBV replication, prevent the progression of liver disease and thereby the development of cirrhosis, liver failure and HCC.

• Interferon alpha (α-IFN) is the first-line treatment option for patients without cirrhosis. Interferon has antiviral, anti-proliferative and immuno-modulatory effects.

• At a dose of 100 mg daily, lamivudine leads to a marked reduction or elimination of detectable HBV DNA in plasma in about 40% of HBeAg positive and 60–70% of HBeAg negative patients.

Vaccines

• Hepatitis B is a vaccine-preventable disease.

• A vaccine for hepatitis B has been available since 1982.

• The Hepatitis B vaccine is safe and effective and is usually given as 3-4 shots over a 6-month period.

- Plasma-derived vaccines.

- Recombinant DNA-derived vaccines.

• The hepatitis B vaccine is the mainstay of hepatitis B prevention.

• WHO recommends that all infants receive the hepatitis B vaccine as soon as possible after birth, preferably within 24 hours.

• Simple environmental procedures can limit the risk of infection to health care workers, laboratory personnel, and others. Examples of specific precautions include the following:

• Gloves should be used when handling all potentially infectious materials.

• protective garments should be worn and removed before leaving the work area.

• masks and eye protection should be worn whenever splashes or droplets from infectious material pose a risk.