Hepatitis, which refers to inflammation of the liver, may be caused by multiple factors; many different viruses, in particular, may cause hepatitis. Letters are used to distinguish the types of viral hepatitis from one another. The most common types in the United States are hepatitis A, B, C, and D. Hepatitis E, which shares features with A, is not endemic to the States. All of the hepatitis viruses can cause an acute inflammation of the liver that lasts several weeks or months and sometimes leads to acute liver failure. Hepatitis B, C, and D viruses can cause chronic, even lifelong hepatitis, resulting in cirrhosis, liver cancer, or liver failure.
Hepatitis viruses have several modes of transmission. Hepatitis A is transmitted by ingestion of food or water that is contaminated with feces from a person infected with the hepatitis A virus. It is diagnosed with a specific blood test. Hepatitis E is also caused by contaminated food and water and can be detected in a blood test or a stool sample. Testing for hepatitis E is generally performed only if a traveler appears to have contracted infection in a country where E is common.
Hepatitis B is transmitted through infected blood, unclean needles, or unprotected sex with a person who has the disease, or by an infected mother to her infant. It, too, is diagnosed with blood tests. Hepatitis C is most often contracted through exposure to contaminated blood, though it can occur as a result of sharing needles, can be passed from mother to newborn, and—rarely—can be contracted through unprotected sex. Hepatitis C is diagnosed with a blood test for antibodies to the virus; however, these may not be detected for a month to a year after a person has contracted the C virus. Hepatitis D is a coinfection that occurs only in the presence of a hepatitis B infection and is transmitted through blood and sexual secretions. Hepatitis D may show up in a hepatitis B carrier or as a coinfection in an individual with hepatitis B.
The Centers for Disease Control and Prevention has estimated that approximately 400,000 to 600,000 people were infected with some type of viral hepatitis during the 1990s. Because fatality from hepatitis is relatively low, mortality figures are a poor indicator of the actual impact of these diseases. Hepatitis is a major public-health issue in the United States and worldwide. In the United States, for example, hepatitis C infection is approximately four times as common as HIV infection.
Vaccines are available to prevent hepatitis A and B. There is no vaccine to prevent hepatitis C. Safe handling of blood products or the injured can reduce the risk of hepatitis C infection. These practices are recommended to healthcare and emergency workers, first responders, and soldiers who encounter blood daily and are at high risk for hepatitis C. Vaccination for hepatitis B also prevents D.
Each year, some 30 million people travel to countries where hepatitis viruses are widespread or epidemic. Travelers need to take special precautions against ingesting these viruses in tap water, ice, raw and unpeeled fruits and vegetables, and raw or partially cooked shellfish and other foods. With care, proper hygiene, frequent hand-washing, safe sex practices, and widespread use of the available vaccines, the majority of viral hepatitis cases are preventable.
This section contains additional explanations of hepatitis B and hepatitis D. It also discusses:
Overview of Hepatitis B
Hepatitis B is a viral infection of the liver, and the ninth leading cause of death. An estimated 2 billion people have been infected with the hepatitis B virus worldwide, and some 300 million are chronically infected and become carriers of the virus. In the United States about 1 in 20 people has been infected—some 1.2 million chronically—and is a carrier of the virus. Hepatitis B accounts for roughly 17,000 hospitalizations and 5,500 deaths in the nation yearly.
The hepatitis B virus is transmitted when infected blood or bodily fluids pass through the skin or mucous membranes of an uninfected person. Transmission can occur through unprotected sex, intravenous drug use, unintended needle sticks, exposure to contaminated blood in healthcare or correctional settings or during accidents and disasters, or even through tattooing and piercing. Infected women also pass the virus to their newborns during childbirth.
The incubation period after exposure to the virus ranges from 60 to 180 days, averaging about 75 days, followed by onset of the illness. Hepatitis B is diagnosed with a panel of simple blood tests; however, it takes four to six weeks after exposure for the virus to be detected in blood.
In its acute stage, hepatitis B may cause mild symptoms of fatigue, fever, joint and muscle pain, and loss of appetite and is sometimes mistaken for the flu. Less common but more serious symptoms also include severe nausea and vomiting, a swollen stomach, and jaundice, or a yellowing of the skin and eyes. These symptoms require immediate medical attention. For some people, hepatitis B is a "silent infection" and results in no symptoms. Infected individuals without symptoms feel well and do not realize they have hepatitis B. These people may unknowingly pass the infection on to others.
Some 90 percent of healthy adults who become infected with hepatitis B recover fully and develop antibodies to protect against future hepatitis B infections. Only a small number, about 5 to 10 percent, will be unable to clear the virus from their bodies and will develop a chronic infection. A blood test six months after diagnosis that still shows the presence of the virus indicates a chronic infection. Adults taking steroids or those with a serious underlying illness, such as kidney disease, are at greatest risk of chronic infection.
However, infants and young children are far more adversely affected by hepatitis B than are adults. Nearly all newborns who are infected with hepatitis B will develop chronic infections. Among young children, the chronicity rate is about 70 percent. For this reason, hepatitis B immunization is recommended by the Centers for Disease Control and Prevention for all infants and young children.
People suffering chronic hepatitis B have a high risk of serious complications. Some 15 to 25 percent die prematurely of liver cancer or cirrhosis—scarring that irreversibly damages the liver and impairs function. Hepatitis B is 100 times more infectious than the AIDS viruses, yet a safe and effective vaccine can prevent most cases of this illness. Not only is vaccination now standard for infants and young children in the United States; it is highly recommended for household contacts and sexual partners of anyone suffering from chronic hepatitis B. Vaccination is the only effective way to prevent the spread of the hepatitis B virus.
Overview of Hepatitis D
Hepatitis D is another type of viral infection of the liver that exists only in the presence of hepatitis B. People who are infected with hepatitis B can also become infected with hepatitis D at the same time. Individuals with a B and D coinfection often suffer more severe symptoms of illness and have a higher risk of liver failure than those with hepatitis B alone. Among people with chronic hepatitis B who are later infected with hepatitis D, a "superinfection" develops. Cirrhosis may occur more often in those with a "superinfection."
Hepatitis D is spread in the same way as hepatitis B, through exchange of infected blood or bodily fluids. Unprotected sex and intravenous drug use put people at high risk of infection. Settings where blood may be exchanged, such as healthcare institutions or tattoo parlors, provide an environment for hepatitis D transmission as well. The infection can also be passed from infected mothers to their newborns.
The only way to prevent hepatitis D is to prevent hepatitis B through vaccination.
Anatomy
The liver is an organ essential to life. It weighs about 3 pounds in women and 4 pounds in men. It is located underneath the ribs and extends horizontally from the middle of the body to the right side. Its surface is smooth and convex. It consists of a myriad of microscopic units called lobules.
The liver stores vitamins, sugar, and iron. It controls production and removal of cholesterol. It clears the body of wastes and poisons and removes bacteria from the bloodstream to combat infection. It releases bile, a substance necessary for digestion and absorption of key nutrients. In addition, it converts nutrients into clotting factors, to stop excessive bleeding, and immune factors to fight foreign invaders.
If the liver fails, a person can live only a day or two. But if even as much as 75 percent to 80 percent of it is removed or destroyed acutely in a healthy individual, the liver will grow new, healthy liver cells and continue to perform its essential functions.
Causes
Both hepatitis B and D viruses are transmitted by the introduction of infected blood or other body fluids through the skin or mucous membranes into the body of an uninfected person. Transmission can occur during sexual relations; through injection with drugs; by sharing personal care items, such as a toothbrush, razor, or nail clipper; or by direct contact with blood or body fluids from an infected person, as in a hospital. Pregnant women can pass the virus to their babies.
Many cases of acute hepatitis B occur sporadically without any known source.
Infections may be acquired at birth or during early childhood. Perinatal or early infection has declined as a result of passive immunization with HBV immune globulin in high-risk situations and the initiation of universal HBV vaccination at birth. Infection control practices, changes in blood donation screening, and blood transfusion protocols have also contributed to the decline in the incidence of hepatitis B.
In the United States, hepatitis B viral infection occurs primarily in adults and adolescents. In Asian countries, the infection occurs most often during childhood through child-to-child or mother-to-child transmission.
Risk Factors
Risk factors for hepatitis B infection include a variety of activities or settings where infected blood or bodily fluids can be exchanged. These include:
Sex: Multiple sexual partners, unprotected sex, and men who have sex with men are at increased risk of hepatitis B infections. The risk of infection is notably high in promiscuous homosexual men, but it is also transmitted sexually from men to women and women to men. Transmission is probably prevented by correct use of condoms.
People who are married to or have sexual relationships with heterosexuals or homosexuals who have chronic hepatitis B infections are also at high risk and should be vaccinated. Sexually active teens who may lack knowledge of the virus and fail to use protection during sex are at high risk.
Drug use: Injecting drugs, particularly using shared needles, puts a person at very high risk of contracting hepatitis B.
Healthcare employment: Doctors, nurses, first responders, emergency technicians, or other health and emergency workers who are exposed to blood are at high risk of infection and should be vaccinated against hepatitis B.
Social service settings: Staff and residents in facilities for the developmentally disabled, in group homes, or in correctional institutions are also at risk and should be vaccinated.
Kidney disease: Patients with kidney disease and those undergoing dialysis are at increased risk of infection.
Household contacts: Living in the household of someone with chronic hepatitis B often results in infection, particularly if there is sharing of nonsterilized personal care items.
War and natural disasters: War and natural disasters may expose individuals to contaminated blood and fluids. Soldiers and relief workers often serve in countries where hepatitis B is endemic.
Foreign travel: Travelers to regions where hepatitis B is common (Asia, Africa, South America, the Pacific Islands, eastern Europe, and the Middle East) should be vaccinated to prevent infection.
Adoption: Families considering adoption, either domestic or international, should be vaccinated. Studies show that asymptomatic adoptees, particularly from countries where hepatitis B is widespread, can infect the family.
Tattoos, piercings, beauty treatments: Body piercing, using improperly sterilized equipment during medical or beauty procedures (such as manicures or pedicures), or tattooing with potentially contaminated needles or ink can lead to hepatitis B infection.
Last reviewed on 7/23/09
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