Hepatitus Viruses

Introduction
There are five main hepatitis viruses (types A, B, C, D and E) that infect the liver. F and G are not considered to be dangerous. Only hepatitis B (and hepatitis F) viruses are DNA viruses; the remaining types are RNA viruses. All hepatitis viruses are parenteral transmission except for A and E, which are fecal-oral transmission.

Symptoms
Acute (lasting fewer than 6 months)
Initial non-specific flu-like symptoms. May include fatigue, fever, headache, muscle and joint aches, coughing, vomiting, and diarrhea. Many hepatocyte death results in the release of high levels of cell enzymes AST and ALT. Some pericanalicular (bile duct lining) cell death results in low levels of GGT and alkaline phosphatase. The presence of these enzymes in the blood is a sign of hepatitis.

As the liver swells, the bile duct becomes blocked, causing a backup of bilirubin to the blood. In 1-2 weeks, the buildup of bilirubin leads to jaundice due to the liver's failure to metabolize and excrete bilirubin.

Chronic
Often asymptomatic, with enlarged liver and mildly elevated liver enzyme levels in the blood. A first-time, acute hepatitis infection can become chronic if the virus is not cleared in 6 months.

HAV
Frequently affects young children. Transmitted by fecal-oral route from poor hand washing, or from ingesting contaminated water.

HBV
Virus lives in all fluids of an infected patient. Transmitted by blood and sexual contact. Only 10% develop chronic hepatitis.

HCV
Leading cause of chronic hepatitis in the United States. 85% develop chronic hepatitis from acute infections. Transmitted parenterally primarily via injections from drug use.

HDV
Replicates only with the help of HBV by using the envelope of HBV to cause infection. An HDV infection to a chronic HBV carrier results in severe acute hepatitis. As carriers can't make antibodies against HBV, they also become carriers of HDV.

HEV
Similar to HAV. Endemic to Asia, India, Africa, and Central America.