There are five primary types of viral hepatitis: A, B, C, D and E. Hepatitis A (HAV) is caused by eating food or drinking water contaminated with the feces of a person infected with hepatitis A virus. For example, people can contract hepatitis A by eating raw or undercooked seafood harvested from contaminated waters, by eating produce that was fertilized with human waste, by eating at restaurants where employees did not wash their hands after using the restroom or even by touching their mouth after shaking hands with an infected person. Anal-oral contact can also cause hepatitis A. Hepatitis A is rarely passed from a mother to her baby. It may play a role in premature labor.

Although hepatitis A causes the liver to swell, the damage is not usually permanent, and the condition generally improves on its own. About 15 percent of patients may have prolonged or relapsing symptoms over a six- to nine-month period, according to the U.S. Centers for Disease Control and Prevention (CDC). However, hepatitis A does not develop into a chronic form of the virus. After a person recovers from hepatitis A, the virus no longer remains in the body and the person cannot become infected with hepatitis A again. However, they may remain vulnerable to infections from other forms of hepatitis.

Hepatitis B (HBV) is caused by contact with bodily fluids of a person infected with the hepatitis B virus. It can be contracted by having sexual intercourse or (in intravenous drug users) through sharing needles with an infected person. It can also be transmitted from an infected mother to her baby during childbirth.

About 1.25 million people are chronically infected with the virus in the United States, according to the CDC. It is about 100 times more infectious than the human immunodeficiency virus (HIV), which causes acquired immune deficiency syndrome (AIDS).

Hepatitis B causes the liver to swell, and in some cases liver damage occurs. It also raises the risk for infection with hepatitis C and HIV. In most cases, the body rids itself of the virus after several months, and the body becomes immune to further hepatitis B viral infections. However, in other cases, the infection may become chronic, scarring the liver (cirrhosis), causing liver failure or causing liver cancer.

According to the CDC, the risk of chronic infection with hepatitis B decreases with age, affecting very few individuals over the age of 5. Chronic infection occurs in:

• 90 percent of infants infected at birth
• 30 percent of children infected between ages 1 and 5
• 6 percent of people infected after age 5

Approximately 15 percent to 25 percent of patients with chronic hepatitis B infection die from the disease.

Of all the hepatitis viruses, hepatitis B poses the greatest risk in pregnancy. In some cases, mothers with hepatitis B transmit the infection to their child when their infected blood enters the baby’s body during the birthing process. In other cases, the child may obtain the virus during the pregnancy. There are no treatments to prevent this from happening. According to the March of Dimes Birth Defects Foundation, up to 20,000 women with hepatitis B give birth each year.

Mothers who have hepatitis B can breastfeed their child as long as the baby receives a shot called HBIG (hepatitis B immune globulin) and a shot of hepatitis B vaccine within the first 12 hours after birth.

Hepatitis B shots help the baby fight off the virus and make the baby much less likely to get the infection. Without treatment, approximately half of babies of mothers with hepatitis B may acquire the infection, according to the March of Dimes Birth Defects Foundation. The majority of these babies become lifelong carriers of the virus, with a high risk of developing serious liver disease and liver cancer as adults.

The shots are administered in three stages:

• At birth – hepatitis B vaccine and HBIG shot
• 1 month to 2 months old – hepatitis B vaccine
• 6 months old (not before 24 weeks, but not after 6 months) – hepatitis B vaccine

Hepatitis C (HCV) is most often transmitted through sharing needles with an infected person during illegal drug use or through other contact with infected blood. Less commonly, it is spread through sexual contact or to dialysis patients by contaminated equipment. The virus can also be transmitted from mother to child during childbirth, although this is rare. An estimated 4.1 million Americans are infected with hepatitis C, and 3.2 million Americans are chronically infected with the virus, according to the CDC.

During the 1970s and 1980s, researchers were aware of transmission of what was called 'non-A, non-B hepatitis.' Many people contracted it from blood transfusions during surgery. This virus was identified as hepatitis C in the late 1980s and screening for it in the blood supply began in the early 1990s.

Hepatitis C is the leading reason for cirrhosis, liver cancer and liver transplants in the United States, according to the U.S. Department of Health and Human Services. In some cases, hepatitis C gets better on its own. However, the virus kills between 1 percent and 5 percent of those infected with it. People with hepatitis C infections are at higher risk for being infected with hepatitis B or HIV.

Hepatitis D (HDV) is caused by contact with a person infected with this virus. It can occur through having sex or sharing needles with an infected individual. Hepatitis D can also be transmitted from an infected mother to her baby during childbirth. However, a person must be positive for hepatitis B to become infected with hepatitis D.

Hepatitis D causes swelling of the liver and it can lead to liver disease and cirrhosis. Acute liver failure is more likely in patients with hepatitis D than in those who have hepatitis B alone. In some cases, hepatitis D resolves on its own.

Hepatitis E (HEV) occurs after consuming food or water contaminated with feces from an infected person. The risk of infection is higher in areas of the world outside the United States that have high rates of hepatitis E infection. Hepatitis E cannot develop into a chronic infection.

Hepatitis E causes swelling of the liver, but usually does not do permanent damage and goes away on its own. However, pregnant women and their babies are at increased risk of dying from infection. Pregnant women are especially at risk during their third trimester. The mortality rate among pregnant women is 20 percent, according to the National Women’s Health Resource Center.

In some cases, viral hepatitis cannot be attributed to any of these primary types. Such cases are classified as non-A-E hepatitis. The cause of this form of hepatitis remains unknown.