What are the differences between hepatitis A, B, and C?

What is hepatitis?
Hepatitis refers to inflammation and damage to the liver. The most common cause of hepatitis is a viral infection, particularly from the hepatitis A, B, and C viruses, but also including the less common hepatitis D and E viruses (1). Autoimmune hepatitis and excessive alcohol and drug intake are also causes of hepatitis. This article focuses on the similarities and differences between hepatitis A, B, and C, which account for the majority of hepatitis cases.

Functions of the liver
The liver damage associated with hepatitis results in multiple different symptoms, because the liver performs many critical functions, including:

  • Bile production for digestion
  • Filtering of toxins
  • Metabolism of carbohydrates, fats, and proteins
  • Activation of enzymes
  • Storage of various mineral and vitamins
  • Synthesis of blood proteins and clotting factors. 

Hepatitis transmission
Hepatitis A is generally transmitted by the consumption of food or water contaminated with faeces from an infected individual, or through close direct contact with an infectious individual (e.g. oral-anal sex) (2).

Hepatitis B is transmitted through contact with infectious body fluids, including blood, vaginal secretions, and semen. The most common source of transmission is from an infected mother to her child during childbirth. Risk factors for hepatitis B include using injectable drugs, sexual intercourse with an infected partner, and sharing razors (or other products that may have come into contact with blood) from an infected individual (3).

Hepatitis C is usually transmitted through exposure to blood from an infected individual, most commonly through sharing needles. Other potential sources of infection include at birth, sexual intercourse, healthcare exposures, blood transfusions and organ transplants, unregulated tattoos or body piercings, and sharing personal items that have been contact with infected blood (4). 

What are the symptoms of hepatitis?
Many individuals with hepatitis do not show any symptoms or only mild symptoms. Symptoms can include:

  • Fever
  • Loss of appetite
  • Diarrhea
  • Nausea
  • Abdominal pain
  • Dark urine
  • Jaundice

Hepatitis A is an acute (short-term) illness, which does not cause chronic liver disease, and is rarely fatal. However, it can still cause debilitating symptoms resulting in significant economic and social consequences, as it is one of the most frequent causes of foodborne infection. Infected children under six years of age often don’t experience any noticeable symptoms, while older children and adults are more likely to suffer from severe symptoms. The incubation period (time from exposure to onset of symptoms) is usually 14-28 days (2).

Hepatitis B can result in a chronic infection that can develop into cirrhosis or liver cancer. The most at-risk individuals for a chronic infection are infants and young children, with 80-90% of infected infants and 30-50% of infected children under 6 years of age developing a chronic infection. Less than 5% of infected adults will develop a chronic infection, assuming they have no other health complications. The incubation period of the hepatitis B virus is 75 days on average, but can vary from 30 to 180 days (3).  

Hepatitis C can develop into a chronic infection (>50% of infected individuals) (5). Most individuals with chronic hepatitis C also remain asymptomatic or only show general symptoms such as fatigue or depression. Over several decades mild to severe liver disease develops in most affected individuals, including cirrhosis (5-25% of cases) and liver cancer (6). Several factors increase the risk of the development of cirrhosis in infected individuals, including being male, >50 years, increased alcohol consumption, hepatitis B or HIV coinfection, and immunosuppressive therapy (6). Chronic hepatitis C is a common reason for a liver transplant in the United States (7).

Treatment and prevention options for hepatitis
Hepatitis A treatment options aim to maintain comfort and adequate nutrition, particularly the replacement of fluids. Although most infections are mild, the recovery can take several weeks to months in some individuals. The majority of infected people develop immunity to further hepatitis A infection. The transmission of hepatitis A can be reduced by provisions of safe drinking water, proper sewage disposal, and following proper hygiene practices. There are also several effective hepatitis A vaccines available (2).

Hepatitis B treatment focuses on maintaining comfort and adequate nutrition for acute infections. Chronic hepatitis B infections can be treated with various medications, including antivirals, to reduce progression of cirrhosis and incidence of liver cancer. However, these treatments do not generally eliminate the hepatitis C virus, so treatment is life-long. Vaccination is the most effective prevention tool for hepatitis B and is included in routine childhood vaccination schedules worldwide (3).

Hepatitis C affected individuals should be provided with a medical evaluation for liver disease, vaccinations for hepatitis A and B, HIV testing, and advice regarding reduced alcohol consumption and weight management for overweight and obese individuals. Affected individuals should not donate blood, tissue, or semen, and refrain from sharing items that may come into contact with blood (e.g. razors, glucose meters, toothbrushes). Any cuts or sores on the skin should be covered to reduce the risk of transmission. There is currently no available vaccine for hepatitis C. It is treated with antiviral medications to eliminate the virus from the body. Newly developed “direct-acting” antivirals have improved treatment considerably with fewer side effects and shorter treatment periods. Nowadays, over 90% of individuals infected with hepatitis C can be cured with 8-12 weeks of oral therapy (8).

References
(1) Hepatitis. from World Health Organization: https://www.who.int/health-topics/hepatitis
(2) Hepatitis A. (2020, July). World Health Organization: https://www.who.int/news-room/fact-sheets/detail/hepatitis-a
(3) Hepatitis B. (2020, July). World Health Organization: https://www.who.int/news-room/fact-sheets/detail/hepatitis-b
(4) Viral Hepatitis – Q&As from the Public. (2020, July). CDC: https://www.cdc.gov/hepatitis/hcv/cfaq.htm
(5) Liang TJ, Rehermann B, Seef LB, & Hoofnagle JH (2000). Pathogenesis, natural history, treatment, and prevention of hepatitis C. Ann Intern Med, 132 (4), 296-305.
(6) Thomas DL, & Seef LB. (2005). Natural history of hepatitis C. Clin Liver Dis, 9 (3), 383-398.
(7) Definition & Facts of Liver Transplant. (2017, March). National Institute of Diabetes and Digestive and Kidney Diseases: https://www.niddk.nih.gov/health-information/liver-disease/liver-transplant/definition-facts
(8) Initial Treatment of Adults with HCV Infection. (2020, August). AASLD: https://www.hcvguidelines.org/treatment-naive