Hepatitis B
Hepatitis B
Disease History, Characteristics, and Transmission
Introduction
Hepatitis B (HBV) is one of six viruses which cause hepatitis, an inflammation of the liver. Formerly known as post-transfusion or serum hepatitis, HBV is transmitted through infected blood and other body fluids, rather than by food or casual contact. Infection can cause acute disease, with symptoms including nausea, malaise, diarrhea, joint pain, and abdominal pain. In some cases, HBV infection progresses to chronic disease, damaging the liver and causing cirrhosis and liver cancer, which may be fatal. In countries where HBV infection is common, liver cancer rates are relatively high. Since the advent of screening of blood for HBV in developed countries, rates of infection have gone down, although people are still at risk through injecting drug use and sexual contact. An effective vaccine helps to protect babies from mother-to-child transmission and to stop those who work with blood from being infected with HBV through accidental exposure.
WORDS TO KNOW
CIRRHOSIS: Cirrhosis is a chronic, degenerative, irreversible liver disease in which normal liver cells are damaged and are then replaced by scar tissue. Cirrhosis changes the structure of the liver and the blood vessels that nourish it. The disease reduces the liver's ability to manufacture proteins and process hormones, nutrients, medications, and poisons.
INTRAVENOUS: It the vein. For example, the insertion of a hypodermic needle into a vein to instill a fluid, withdraw or transfuse blood, or start an intravenous feeding.
JAUNDICE: Jaundice is a condition in which a person's skin and the whites of the eyes are discolored a shade of yellow due to an increased level of bile pigments in the blood resulting from liver disease. Jaundice is sometimes called icterus, from a Greek word for the condition.
Disease History, Characteristics, and Transmission
HBV is unrelated to any known human virus, although similar liver viruses are found in other animal species. It exists as spherical particles with double stranded DNA as the genetic material. Around 70% of those infected with HBV will develop symptoms around 12 weeks after exposure. These symptoms include nausea, diarrhea, joint pain, abdominal discomfort, fatigue, and loss of appetite. Jaundice—a yellowing of the skin and whites of the eyes—may develop, along with dark urine and clay colored stools. The symptoms may continue for several months. In around 10 percent of cases, the HBV infection causes chronic viral hepatitis. Around 15–25 percent of those who develop chronic HBV will die of the disease, through cirrhosis (scarring) of the liver or liver cancer.
Transmission of HBV occurs through infected blood and other body fluids. Sex contact with an infected person, or injecting drug use with sharing of needles and other items, is strongly associated with HBV transmission. The virus is highly infectious; experiments have shown that it can be spread through a mere 0.0001 ml of blood. But for most people the HBV infection clears up within a few weeks. However, those with chronic disease remain infectious, even if they do not have symptoms. HBV infection can also pass from mother to child through contact with infected blood during childbirth.
Scope and Distribution
The Centers for Disease Control and Prevention (CDC) recorded 5,494 cases of acute HBV infection in the United States in 2005. Using this data, the CDC predicted that there were around 51,000 total new HBV infections that year. The incidence of infection is on the decline in the United States, but there are 1.25 million people already carrying the infection. Each year, between 3,000 and 5,000 people in the United States die of complications of chronic HBV infection such as liver cirrhosis and liver cancer.
IN CONTEXT: SOCIAL AND PERSONAL RESPONSIBILITY
The National Center for HIV, STD, and TB Prevention, Divisions of HIV/AIDS Prevention at Centers for Disease Control and Prevention (CDC) states that the following are the best practices to reduce the risk of contracting Hepatitis B:
- “Hepatitis B vaccine is the best protection.
- If you are having sex, but not with one steady partner, use latex condoms correctly and every time you have sex. The efficacy of latex condoms in preventing infection with HBV is unknown, but their proper use may reduce transmission.
- If you are pregnant, you should get a blood test for hepatitis B; Infants born to HBV-infected mothers should be given HBIG (hepatitis B immune globulin) and vaccine within 12 hours after birth.
- Do not shoot drugs; if you shoot drugs, stop and get into a treatment program; if you can't stop, never share drugs, needles, syringes, water, or ‘works,’ and get vaccinated against hepatitis A and B.
- Do not share personal care items that might have blood on them (razors, toothbrushes).
- Consider the risks if you are thinking about getting a tattoo or body piercing. You might get infected if the tools have someone else's blood on them or if the artist or piercer does not follow good health practices.
- If you have or had hepatitis B, do not donate blood, organs, or tissue.
- If you are a health care or public safety worker, get vaccinated against hepatitis B, and always follow routine barrier precautions and safely handle needles and other sharps.”
Infants are most at risk of developing chronic HBV infection even though they are unlikely to have symptoms of acute disease. Others at high risk include sex and household partners of those with chronic HBV, men who have sex with men (especially if they have more than one sexual partner), intravenous drug users, and people whose work brings them into contact with blood, such as healthcare workers.
Around 10% of those with the human immunodeficiency virus (HIV) are also chronic carriers of HBV. The risk of HBV infection has also been shown to be higher among those whose parents were born in Southeast Asia, Africa, the Amazon basin, the Pacific Islands, and the Middle East. Rates of HBV in part of Africa and Asia are high and liver cancer accounts for 20–30 percent of all cancer cases in these areas.
Treatment and Prevention
There is no specific treatment for acute HBV infection once acquired. Adequate nutrition and rest are most often recommended to ease symptoms. Chronic infection can be treated with interferon, an immune system protein, and antiviral drugs such as lamivudine.
The hepatitis B vaccine is manufactured through genetic engineering, a process that involves inserting the HBV gene into yeast cells. It was introduced in 1982 and is highly effective against infection. The vaccine is now recommended for all newborns. Adults with an increased risk of exposure to HBV through work, travel, sexual practices, or drug use are also encouraged to get vaccinated.
Impacts and Issues
HBV is a bloodborne infection. Those who are, or have been, infected should not donate blood, organs, or tissue. People should not share razors or toothbrushes, which may carry invisible traces of blood. People who inject drugs should never reuse or share needles. Needle exchange programs in some countries have demonstrated limited success in reducing incidence of HBV among intravenous drug users.
Nearly one million people die each year from cirrhosis or liver cancer caused by HBV. Deaths from HBV-related illnesses disproportionately affect the developing world. HBV is endemic in some regions. In China, as much as 10 percent of the population is HBV infected. In certain parts of Eastern and Southeast Asia, 7–10 percent of all pregnant women are infected; 70–90 percent of the children born to these women become infected during childbirth. Though HBV is vaccinepreventable, the vaccine remains significantly more costly than other childhood vaccines.
Though most HBV infections are acquired during infancy or childhood, HBV has life-long effects. The social and economic effects of populations with high rates of HBV infections are substantial. Care of patients with chronic HBV is costly. HBV is one of the few viruses that can lead to cancer, although the way in which it does so is not well understood. HBV-related liver cancer and cirrhosis increase demand for liver transplants in an environment already strained by a lack of suitable donor organs. If the HBV vaccine could be made more readily available in those countries where infection is common, it could reduce the number of cases of liver cancer among the population.
See AlsoBlood Supply and Infectious Disease; Bloodborne Pathogens; Hepatitis C.
BIBLIOGRAPHY
Books
Koff, R.S., and G.Y. Wu. Chronic Viral Hepatitis. Totowa: Humana Press, 2002.
Wilson, Walter R., and Merle A. Sande. Current Diagnosis & Treatment in Infectious Diseases. New York: McGraw Hill, 2001
Web Sites
Centers for Disease Control and Prevention (CDC). “Hepatitis B Fact Sheet.” November 7, 2006 <http://www.cdc.gov/hepatitis> (accessed April 25, 2007).