Hepatitis: Videos & Practice Problems

Hepatitis is defined as inflammation of the liver, which can result from various causes including viral infections. The five main types of viral hepatitis—hepatitis A, B, C, D (delta), and E—are contagious and primarily cause similar symptoms such as fever, jaundice (yellowing of the skin and eyes due to bilirubin buildup), loss of appetite, joint pain, abdominal pain, fatigue, and discolored bowel movements. Bilirubin is a byproduct of cellular breakdown normally processed by the liver, so impaired liver function leads to its accumulation, causing jaundice.

Chronic infection is a critical concern with hepatitis because persistent viral presence can lead to cirrhosis, characterized by liver tissue death, scarring, liver failure, and increased risk of liver cancer. Understanding the differences among the hepatitis viruses is essential for diagnosis, treatment, and prevention.

Hepatitis viruses are named sequentially as A, B, C, D (delta), and E, often abbreviated as HAV, HBV, HCV, HDV, and HEV respectively. Hepatitis delta is unique because it cannot infect independently; it requires co-infection with hepatitis B virus. HDV is a satellite virus that hijacks the molecular machinery of HBV to replicate, meaning infection with HDV only occurs in the presence of HBV.

The transmission routes of hepatitis viruses fall into two main categories: fecal-oral contamination and blood or bodily fluid exposure. Hepatitis A and E are transmitted via the fecal-oral route, often through contaminated food or water. In contrast, hepatitis B, C, and D are bloodborne pathogens, transmitted through exposure to infected blood or bodily fluids, including sexual contact and needle sharing. A helpful mnemonic is that hepatitis A and E are associated with "ate" (fecal-oral), while B, C, and D are bloodborne.

Regarding chronic infection potential, bloodborne hepatitis viruses (B, C, and D) are capable of causing chronic infections, which can persist and lead to severe liver damage. Hepatitis A and E typically cause acute infections that resolve without chronicity, although hepatitis E can rarely become chronic in immunocompromised individuals, such as organ transplant recipients on immunosuppressants.

Chronic hepatitis infections increase the risk of liver cancer. Therefore, hepatitis B, C, and D infections are linked to a higher likelihood of developing hepatocellular carcinoma. Hepatitis D exacerbates the severity of hepatitis B infections, increasing the risk of cancer. Hepatitis A and E generally do not cause cancer, except in rare chronic hepatitis E cases.

Vaccination is a key preventive measure. Vaccines are available for hepatitis A and B and are included in routine childhood immunization schedules. There is no vaccine for hepatitis C, but antiviral treatments have been developed that can effectively cure chronic hepatitis C infections. No vaccine exists for hepatitis D; however, preventing hepatitis B infection through vaccination also prevents hepatitis D since HDV requires HBV for infection. Similarly, there is no vaccine for hepatitis E.

Hepatitis viruses can be categorized based on their modes of transmission, potential to cause cancer, and availability of vaccination. Hepatitis A and E are primarily transmitted through fecal-oral contamination, which means they spread via ingestion of contaminated food or water. A helpful mnemonic to remember this is the phrase "I ate it," highlighting the presence of the letters "A" and "E" in both the phrase and the virus names. In contrast, hepatitis B, C, and D (also known as delta) are transmitted through blood, making bloodborne transmission their primary route.

When considering the potential to cause cancer, it is important to note that viruses causing chronic infections are more likely to lead to cancer development. Since hepatitis B, C, and D are bloodborne and can establish chronic infections, they have the potential to cause liver cancer. Hepatitis B is particularly significant in this regard, and hepatitis D, which requires co-infection with hepatitis B, can exacerbate the risk of cancer. Hepatitis C also carries a risk of cancer due to its chronic nature.

Vaccination is available for hepatitis A and B viruses. Immunization against hepatitis B also indirectly protects against hepatitis D, as the delta virus depends on hepatitis B for replication. No vaccines currently exist for hepatitis C or E, making prevention strategies for these types more reliant on avoiding exposure.

Understanding these distinctions is crucial for effective prevention, diagnosis, and management of hepatitis infections, emphasizing the importance of vaccination and awareness of transmission routes in reducing the global burden of hepatitis-related diseases.