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HEPATITIS B
Hepatitis B is an infectious illness caused by(HBV) which infects theof
, including humans, and causecalleiginally known as
"serum hepatitis", the disease has cain parand it quarter of the than 2 billion people have been
infected with the hepatitis B virus. This includes 350 millof the virus.
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 titer DNA in serum. Perinatal infection is a major route of infection in
endemic (mainly developing) countries. Other risk factors for developing HBV infection include
working in a healthcare setting, transfusions and dialysis, acupuncture, tattooing, extended
overseas travel, and residence in an institution. However, hepatitis B viruses 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 and rarely, death. Chronic hepatitis B may eventually cause liverana fatal disease with very poor response to current chemotherapy. The infection is preventable by Hepatitis B virus is a- hepa from hepatatrophic and dna because it iand it has a circularcomposed of partially double-stranded viruses through aintermediate form bynd in this respect they are similalthough replication takes place in the liver, the virus spreads to the blood where virus-specific proteins and their correspondingare found in infected people. Blood tests for these proteins and antibodies are used to diagnose the infection. Signs and symptoms
Acute infection with hepatitis B virus is associated with acute vira– an illness that begins with general ill-health, loss of appetite, nausea, vomiting, body aches, mild fever, dark urine, and then progresses to development ofIt has been noted that itchy skin has been an indication as a possible symptom of all hepatitis virus types. The illness lasts for a few weeks and then gradually improves in most affected people. A few patients may have more severe liver diseasend may die as a result of it. The infection may be entirely asymptomatic and may go unrecognized. Chronic infection with hepatitis B virus may be either asymptomatic or may be associated with a chronic inflammation of the liver (chronic hepatitis), leadingover a period of several years. This type of infection dramatically increases the incidence o(liver cancer). Chronic carriers are encouraged to avoid consuming alcohol as it increases their risk forand liver cancer. Hepatitis B virus has been linked to the development of (MGN). MECHANISMS
Pathogenesis
Hepatitis B virus primarily interferes with the functions of the liver by replicating in liver cells, known aheis not yet known, though there is evidence that the receptor in the closely relateBV virions (DANE particle) bind to the host cell via the preS domain of the viral surface antigen and are subsequently internalized by endocytosis. PreS and IgA receptors are accused of this interaction. HBV-preS specific receptors are primarily expressed on hepatocytes; however, viral DNA and proteins have also been detected in extrahepatic sites, suggesting that cellular receptors for HBV may also exist on extrahepatic cells. During HBV infection, the hostcauses both hepatocellular damage and viral clearance. Although the innate immune response does not play a significant role in these processes, the adaptive immune response, particularly virus-specific(CTLs), contributes to most of the liver injury associated with HBV infection. CTLs eliminate HBV infection by killing infected cells and producing antivirawhich are then used to purge HBV from viable hepatocytes. Although liver damage is initiated and mediated by the CTLcan worsen CTL-induced immunopathology, and activated at the site of infection may facilitate the accumulation of CTLs in the liver. Transmission
Transmission of hepatitis B virus results from exposure to infectious blood or body fluids containing blood. Possible forms of transmission inc& syringes, afrom mother to child during childbirth. Without intervention, a mother who is positive for HBsAg confers a 20% risk of passing the infection to her offspring at the time of birth. This risk is as high as 90% if the mother is also positive for HBeAg. HBV can be transmitted between family members within households, possibly by contact of nonintact skin or mucous membrane with secretions or saliva containing HBV. However, at least 30% of reported hepatitis B among adults cannot be associated with an identifiable risk factor.
Prevention
Severahave been developed for the prevention of hepatitis B virus infection. These rely on the use of one of the viral envelope proteins (hepatitis B surface antigen or HBsAg). The vaccine was originally prepared from plasma obtained from patients who had long-standing hepatitis B virus infection. However, currently, it is made using a synthetictechnology that does not contain blood products. One cannot be infected with hepatitis B from this vaccine. The risk of vertical transmission to the newborn can be drastically reduced from 20%-90% to 5%-10% by administering to the newborn hepatitis B vaccine (HBV 1) and hepatitis B immune globulin (HBIG) within 12 hours of birth, followed by a second dose of hepatitis B vaccine (HBV 2) at 1-2 months and a third dose at and no earlier than 6 months (24 weeks). Since 2% of infants vaccinated will not develop immunity after the first three dose series, infants born to hepatitis B positive mothers are tested at 9 months for hepatitis B surface antigen (HBsAg) and the antibody to the hepatitis B surface antigen (anti-HBs); if post-vaccination test results indicate that the child is still susceptible, a second three dose series at (0, 1 and 6 months) is administered. If the child is still susceptible after the second series, a third series is not recommended. Following vaccination, hepatitis B surface antigen may be detected in serum for several days; this is known as vaccine antigenemia. The vaccine is administered in two-, three-, or four-dose schedules into infants and adults, which provides protection for 85–90% of individuals. Protection has been observed to last 12 years in individuals who show adequate initial response to the primary course of vaccinations, and that immunity is predicted to last at least 25 years. patitis B does not generally spread through water and food. Instead, it is transmitted through body fluids; prevention is thus the avoidance of such transmission: unprotected sexual contact, blood transfusions, re-use of contaminated needles and syringes, and vertical transmission during child birth. Infants may be vaccinated at birth. Shi, et al. showed that besides the WHO recommended joint immunoprophylaxis starting from the newborn, multiple injections of small dose(HBIg, 200–400 IU per month), or oral lamivudine (100 mg per day) in HBV carrier mothers with a high degree of infectiousness (>106 copies/ml) in late pregnancy (the last three months of pregnancy), effectively and safely prevent HBV intrauterine transmission, which provide new insight into prevention of HBV at the earliest stage.

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