Hepatitis

Introduction. 

Hepatitis is an infection of the liver and can be caused by many pathogens. Primary among these pathogens are the hepatitis viruses. Other than the fact that they all infect and damage the liver, these viruses share few common traits and come from diverse virus families: picornaviruses, hepadnaviruses, flaviviruses and caliciviruses. Hepatitis A and E are enteroviruses and cause generally mild, self-resolving infections. Hepatitis B and C are serious infections transmitted by direct contact (body fluids) and may cause liver cancer and chronic liver disease. Hepatitis D only occurs as a coinfection with HBV and complicates HBV infection. Hepatitis G is a milder form of Hepatitis C. Other viruses, including adenovirus, can also cause hepatitis.

Summary

Cause: Hepatitis A virus (picornavirus)

• Transmission: Fecal-oral
• Symptoms: Generally mild (nausea, vomiting, loss of appetite, fatigue, dark urine, jaundice, enlarged liver)
• Pathogenesis: Infection of hepatocytes eventually stimulates humoral and cellular immunity to destroy infected cells
• Complications: fulminant liver disease with encephalopathy (<1%)
• Treatment: immunoglobulin administration can lessen severity
• Immunity: lifelong
• Vaccine: Yes

Cause: Hepatitis B virus (hepadnavirus)

• Transmission: Body fluids, STD,
• Symptoms: nausea, vomiting, loss of appetite, fatigue, dark urine, jaundice, enlarged liver
• Pathogenesis: Infection of hepatocytes eventually stimulates cellular immunity and inflammation, damaging the cells
• Complications: fulminant liver disease with encephalopathy (<1%); liver cancer; chronic infection leading to cirrhosis; 6,000 deaths per year
• Treatment: immunoglobulin administration can lessen severity
• Immunity: lifelong 
• Vaccine: Yes

Cause: Hepatitis C and G viruses (flavivirus)

• Transmission: Body fluids, STD
• Symptoms: nausea, vomiting, loss of appetite, fatigue, dark urine, jaundice, enlarged liver
• Pathogenesis: Infection of hepatocytes eventually stimulates cellular immunity and inflammation, damaging the cells
• Complications: HCV causes liver cancer (less than HBV) and chronic infection leading to cirrhosis or liver failure; HGV causes chronic infections; est. 8,000 - 10,000 deaths (US)
• Treatment: immunoglobulin administration can lessen severity
• Immunity: lifelong 
• Vaccine: Yes

Cause: Hepatitis D virus (delta agent)

• Transmission: Body fluids, STD
• Symptoms: increased severity of HBV infection
• Pathogenesis: Co-infection with HBV required for HDV to replicate. HDV induces cytotoxic effect and kills liver cells directly
• Complications: fulminant liver disease with encephalopathy  and chronic infection leading to cirrhosis are much more common and severe
• Treatment: treatment of HBV infection
• Immunity: antibodies to HBV give limited protection 
• Vaccine: only vs. HBV

Cause: Hepatitis E virus (calicivirus)

• Transmission: Fecal-oral
• Symptoms: generally mild (nausea, vomiting, loss of appetite, fatigue, dark urine, jaundice, enlarged liver)
• Pathogenesis: Infection of hepatocytes eventually stimulates humoral and cellular immunity to destroy infected cells
• Complications: fulminant liver disease with encephalopathy (1 - 2%) - more serious than HAV; In pregnant women mortality is 20%
• Treatment: immunoglobulin administration less effective than HAV