Overview
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 cause an acute inflammation of the liver that lasts several weeks or months. Hepatitis B, C, and D viruses can cause chronic, even life-long 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 co-infection 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 co-infection in an individual with acute 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 health care 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.
Overview of hepatitis A
Hepatitis A is a viral infection of the liver that accounts for 20 percent to 25 percent of hepatitis cases in developed countries. It is primarily caused by eating food or drinking water contaminated with the feces of a person infected with the hepatitis A virus. A two- or three-dose vaccination for hepatitis A before exposure to the virus prevents the disease for as long as 20 years.
Children who live in areas with high rates of hepatitis A are candidates for routine vaccination. The infection is generally not transmitted through blood and bodily fluids, but it can be, so men who have sex with men and people who use illegal drugs may also want to consider being vaccinated. The Public Health Service also recommends that all people with chronic hepatitis or liver disease of any cause be vaccinated against hepatitis A.
In the United States, there are about 80,000 new cases of hepatitis A each year. The incidence varies widely with age, socioeconomic class, geography, and other factors. Cases of hepatitis A may occur sporadically, one case at a time, or in epidemics. It is a significant risk following natural disasters, particularly floods, when the water and sanitation systems may be compromised. Children in communities with high rates of hepatitis A are vulnerable because they frequently put contaminated food and objects in their mouths.
Hepatitis A causes a sudden severe illness in adults. Symptoms include nausea, vomiting, fatigue, abdominal pain, jaundice, and fever. These generally occur a month, on average, after infection. The infected person can transmit the virus to others for as long as two weeks before any symptoms appear. The majority of children under age six have no symptoms, and may transmit the disease unknowingly. The disease is diagnosed with a specific blood test.
Hepatitis A is almost always a self-limiting illness, which means it generally runs its course over a period of weeks or months, and resolves on its own. Most cases of the hepatitis A last one to two months, but in about 10 percent of cases, symptoms last six months or more. The prognosis is excellent and recovery is complete. Mortality rates for large epidemics are less than 1 per 1,000. (Note: The mortality rate among people over age 50 who contract hepatitis A is higher: about 1.8 percent.) Rarely does Hepatitis A cause liver failure, and it does not lead to development of cirrhosis of the liver or chronic hepatitis.
Overview of hepatitis E
Hepatitis E is also caused primarily by ingesting contaminated food and water, and it takes a course similar to hepatitis A's. It is rare in the United States. This virus is common in India, Pakistan, China, Mongolia, Hong Kong, North Africa, and the southeast Pacific region. In the rural areas of central Mexico and Central American countries it can reach epidemic proportions, posing a special risk to travelers to these nations.
The hepatitis E virus is found in the stool of infected humans, and it primarily affects young adults. Mortality rates in the general population of countries where the virus is endemic are low, ranging between 0.5 percent to 4 percent. But they are much higher for women during pregnancy, as high as 15 to 20 percent. Hepatitis E can also cause fetal complications, especially if it hits during the third trimester of pregnancy. Most patients have a complete recovery without chronic aftereffects.
Need-to-know anatomy
The liver is an organ essential to life. It is about the size of a football, and 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 of it is diseased or destroyed, the liver will grow new, healthy liver cells and continue to perform its essential functions.
Causes
The transmission of hepatitis A and E is primarily through fecal contamination and oral ingestion. Eating food or drinking water that is contaminated with the feces of someone who has Hepatitis A or E is the main source of infections. Poor personal hygiene, poor sanitation, and intimate and/or sexual contact with an infected individual can facilitate transmission. Intravenous drug use also is a risk factor for both hepatitis A and E transmission.
Consumption of contaminated raw or partially cooked shellfish provides a key route of transmission in countries where raw seafood is popular, including the United States. Developing countries commonly experience waterborne and food-borne epidemics of hepatitis A and E. In those countries food, drinks, ice, vegetables, fruit, cooking surfaces, and more may be contaminated with the hepatitis A or E viruses.
Risk Factors
The risk factors for hepatitis A include:
Exposure to contaminated food:
Individuals who often eat raw shellfish, a common mode of transmission, should strongly consider vaccination for hepatitis A. Improper food handling and sanitation practices in restaurants and other institutional eating facilities are other key factors. In addition, significant outbreaks of hepatitis A have been associated with imported fruits and vegetables. In 1997, for example, an outbreak of hepatitis A in schoolchildren was traced back to strawberries imported from Mexico and sold to the National School Lunch program. In 2003, more than 700 residents in 10 states contracted hepatitis A from eating imported green onions.
Exposure to a natural disaster:
Floods in particular can contaminate water supplies and wells and can compromise sanitation systems. Recovery workers in areas where disasters have occurred are at high risk of infection.
Living in close quarters:
People who live in dorms, group homes or nursing homes, correctional institutions, or other housing situations involving close contact with many unrelated individuals are at higher risk of contracting hepatitis A.
Day care:
Children and workers in day-care centers are at high risk of hepatitis A. Some 70 percent of children under the age of 6 have no symptoms when they are infected and so can spread the virus without anyone noticing. Diapering or improper disposal of diapers from children who may have the virus can spread infections. Moreover, children are notorious for putting everything in their mouths.
Travel to developing countries:
Vaccination against hepatitis A is generally recommended when traveling to nations where hepatitis A and E are common. Avoiding tap water, food items washed in tap water, and raw, unpeeled fruits and vegetables is critical to preventing infection.
Drug use:
Intravenous drug use is a risk factor all types of hepatitis. Use of drugs or dietary supplements that can damage the liver can worsen the effect should exposure to the virus occur.
Sexual activity:
Intimate contact with infected people can facilitate transmission of these viruses. Engaging in anal/oral sex increases the risk of infection.
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