What Causes Hepatitis?
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Medically reviewed by Isabel Casimiro, MD, PhD
Hepatitis, also called viral hepatitis, is inflammation of the liver. There are several types of viral hepatitis, including hepatitis A, B, C, D, and E. Different viruses cause each form of hepatitis. Some hepatitis viruses spread through contaminated water or food, while others spread through contact with the bodily fluids (e.g., blood, semen) of a person with hepatitis. When hepatitis viruses enter the body, they attack the liver cells and cause inflammation that can lead to liver damage and other complications.
Causes of Hepatitis A
The hepatitis A virus (HAV) causes hepatitis A—an acute (short-term) and highly contagious liver infection. Hepatitis A spreads through the fecal-oral route, meaning you can get it by ingesting microscopic (very small) amounts of an infected person’s poop. This happens most frequently by consuming contaminated food or water, but can also spread through certain types of sexual contact (e.g., oral or anal sex) or by caring for someone with hepatitis A.
Food can become contaminated with the virus if a person with hepatitis A does not wash their hands before handling food. This can occur anywhere from growing and harvesting food to preparing and serving food. An estimated 1.4 million cases of hepatitis A occur worldwide each year, with most cases occurring in countries that have poor sanitation. In countries where hepatitis vaccines are more widely available, hepatitis A is less common.
Causes of Hepatitis B
The hepatitis B virus (HBV) is highly contagious and spreads through contact with the bodily fluids of a person with hepatitis B, including their blood, semen, saliva, and vaginal fluids. Most cases of hepatitis B spread from person to person through:
Sharing dirty needles (e.g., piercing, tattooing, injected drug use)
Having sex with a person with hepatitis B
Using or sharing items contaminated with the virus, such as razors, toothbrushes, or medical equipment (e.g., syringes or other sharp objects)
Coming into direct contact with open sores or the blood of a person with hepatitis B
Giving birth, meaning that a baby can contract hepatitis B from their birth parent during childbirth
Globally, an estimated 296 million people live with chronic (long-term) hepatitis B, and 1.5 million new cases occur each year. In the United States, an estimated 14,000 people develop acute hepatitis B annually, and about 880,000 people live with chronic hepatitis B.
Causes of Hepatitis C
The hepatitis C virus (HCV) is a bloodborne virus that spreads through contact with infected blood. This can occur through the following methods:
Sharing needles or syringes with a person with hepatitis C
Having blood transfusions with contaminated blood before 1992; modern blood screening methods have significantly reduced the risk of hepatitis C from blood transfusions
Engaging in unprotected sex with a person with hepatitis C
Using personal items contaminated with another person’s blood, such as razors, nail clippers, or toothbrushes
Making contact with the blood or open sores of someone with hepatitis C
During childbirth, when a birthing parent with hepatitis C spreads it to their baby
Hepatitis C can be an acute infection but becomes a chronic, lifelong illness for more than half of the people who are infected and don't receive proper treatment. About 58 million people worldwide live with chronic hepatitis C, with an estimated 1.5 new cases occurring each year.
Causes of Hepatitis D
Hepatitis D virus (HDV) is a unique virus that only affects people with preexisting hepatitis B. The HDV virus is dependent on HBV for its replication—meaning, that in order to develop hepatitis D, you have to have the hepatitis B infection already in your system.
HDV spreads in the same way HBV does, which is through blood or other bodily fluids (e.g., semen or vaginal fluids). You can become infected with hepatitis B and D at the same time or get hepatitis D after having hepatitis B. The latter is known as a “superinfection.” Hepatitis D worsens the severity of hepatitis B and may cause an acute or chronic infection.
Causes of Hepatitis E
The hepatitis E virus (HEV) causes hepatitis E. This infection is a leading cause of acute viral hepatitis in countries with limited access to clean water and sanitation services.
HEV primarily spreads through the oral-fecal route through contaminated food or water. Though less common, HEV can infect animals and spread when people consume undercooked or raw pork, shellfish, or venison (deer meat). Hepatitis E is usually a short-term infection and generally only progresses to chronic hepatitis in organ donor recipients.
Is Hepatitis Hereditary?
Viral hepatitis is not hereditary, though some research suggests that genetics may influence the severity of the disease and the likelihood of an acute hepatitis infection progressing to a chronic illness. Currently, research in this area is ongoing, and limited evidence suggests genetics may play some role in your body's immune response to hepatitis B and C.
Who Gets Hepatitis?
Hepatitis is a global health concern affecting people of all ages and ethnicities. Certain groups have a higher risk of getting viral hepatitis, including the following factors:
Age: People of all ages can get viral hepatitis, but the age at which a person gets viral hepatitis plays a role in whether the infection is acute or chronic. Infants and young children infected with certain types of viral hepatitis (e.g., hepatitis B) are more likely to develop chronic hepatitis than adults.
Sex: People assigned male at birth have higher rates of hepatitis B and C, which can be because males have higher rates of underlying risk factors such as intravenous drug use and riskier sexual practices.
Ethnicity: The prevalence of hepatitis can vary across different ethnic groups due to factors such as access to sanitation and healthcare. In the United States, hepatitis B is more prevalent in certain Asian, Pacific Islander, and African immigrant populations, while hepatitis C is more common among Native Americans and Black people.
Risk Factors
Certain environmental, behavioral, and health factors can also increase your risk of viral hepatitis. These include:
Limited access to clean water or sanitation
Living with someone with hepatitis
Engaging in sex with someone with hepatitis
Using recreational injectable drugs and sharing needles, syringes, or other drug paraphernalia
Traveling to or living in areas with high rates of hepatitis
Working in health care or public safety
Having certain health conditions such as HIV, sexually transmitted infections, liver disease, or kidney failure
Experiencing homelessness
Being incarcerated
A Quick Review
Viral hepatitis is inflammation of the liver. Several viruses cause different types of hepatitis, including hepatitis A, B, C, D, and E. The viruses spread through contaminated food or water or contact with the blood or bodily fluids of someone with hepatitis. Most types of hepatitis are short-term infections, but some can progress to chronic, lifelong illnesses that lead to liver damage.
People of all ages and ethnicities can get viral hepatitis, but the infection is most common in areas with limited access to sanitation and clean water. You can lower your risk of hepatitis by getting vaccinated, practicing good hygiene, and avoiding risky behaviors such as having unprotected sex and sharing needles or syringes with others.
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