Hepatitis B (cont.)

Hepatitis B is spread mainly by exposure to infected blood or body secretions. In infected individuals, the virus can be found in the blood, semen, vaginal discharge, breast milk, and saliva. Hepatitis B is not spread through food, water, or by casual contact.

In the United States, sexual contact is the most common means of transmission, followed by using contaminated needles for injecting illicit drugs, tattooing, body piercing, or acupuncture. Additionally, hepatitis B can be transmitted through sharing toothbrushes and razors contaminated with infected fluids or blood.

Hepatitis B also may be spread from infected mothers to their babies at birth (so-called 'vertical' transmission). This is the most prevalent means of transmission in regions of the world where hepatitis B rates are high. The rate of transmission of hepatitis B from mother to newborn is very high, and almost all infected infants will develop chronic hepatitis B. Fortunately, transmission can be significantly reduced through immunoprophylaxis (see below).

Rarely, hepatitis B can be transmitted through transfused blood products, donated livers and other organs. However, blood and organ donors are routinely screened for hepatitis which typically prevents this type of transmission.

Acute hepatitis B is the period of illness that occurs during the first one to four months after acquiring the virus. Only 30% to 50% of adults develop significant symptoms during acute infection. Early symptoms may be non-specific, including fever, a flu-like illness, and joint pains. Symptoms of acute hepatitis may include:

• fatigue,
  
  
• loss of appetite,
  
  
• nausea,
  
  
• jaundice (yellowing of the skin and eyes), and
  
  
• pain in the upper right abdomen (due to the inflamed liver).

Rarely, acute hepatitis damages the liver so badly it can no longer function. This life-threatening condition is called "fulminant hepatitis." Patients with fulminant hepatitis are at risk of developing bleeding problems and coma resulting from the failure of the liver. Patients with fulminant hepatitis should be evaluated for liver transplantation. Small studies suggest that the drug lamivudine (Epivir), may be of limited assistance in these cases (see below).

What determines the outcome of acute hepatitis B?

The body's immune response is the major determinant of the outcome in acute hepatitis B. Individuals who develop a strong immune response to the infection are more likely to clear the virus and recover. However, these patients also are more likely to develop more severe liver injury and symptoms due to the strong immune response that is trying to eliminate the virus. On the other hand, a weaker immune response results in less liver injury and fewer symptoms but a higher risk of developing chronic hepatitis B. People who recover and eliminate the virus will develop life-long immunity, that is, protection from subsequent infection from hepatitis B.

Most infants and children who acquire acute hepatitis B viral infection have no symptoms. In these individuals, the immune system fails to mount a vigorous response to the virus. Consequently, the risk of an infected infant developing chronic hepatitis B is greater than 95%. In contrast, only 5% of adults who have acute hepatitis B develop chronic hepatitis B.

Source: MedicineNet.com
http://www.medicinenet.com/hepatitis_b/article.htm