Hepatitis B |
OverviewHepatitis B is an infectious liver disease which is caused by a virus. About 3000 cases are reported in Canada annually. However many more cases probably remain unreported. Blood tests suggest that about 5 percent of Canadians have had hepatitis B at some point in their lives. Most people get better and can no longer pass on the virus. CausesHepatitis B is caused by the hepatitis B virus (HBV). Infections of hepatitis B occur only if the virus is able to enter the blood stream and reach the liver. Once in the liver the virus reproduces and releases large numbers of new viruses into the bloodstream. The incubation period (the time between initial contact with the virus and onset of the disease) for hepatitis B ranges from 45 to 180 days with an average of 60 to 90 days. The length of the incubation period depends on the amount of virus to which a person is exposed. Exposure to a large dose of virus results in a short incubation period. Blood is the major source of the hepatitis B virus. It can also be found in other tissues and body fluids but in much lower concentrations. The risk of transmission varies according to the specific source: Blood Direct contact with infected blood can transmit the hepatitis B virus through:
To a lesser extent indirect contact with blood-contaminated surfaces can also transmit the hepatitis B virus. Saliva Saliva of people with hepatitis B can contain the hepatitis B virus but in very low concentrations compared with blood. Injections of infected saliva can transmit the virus so bite injuries can also spread the disease. There are no reports of people getting hepatitis B from mouth contact with infected CPR manikins or mouthpieces of musical instruments. Other Body Fluids and Tissues Hepatitis B is found in semen vaginal secretions and breast milk. The virus can be transmitted during unprotected sexual intercourse and from mother to infant during birth and through breast feeding. Synovial fluid (joint lubricant) amniotic fluid cerebrospinal fluid and peritoneal fluid (found in the abdominal cavity) can contain the hepatitis B virus but the risk of transmission is not known. Feces nasal secretions sputum sweat tears urine and vomit have not been implicated in the spread of hepatitis B. Unless visibly contaminated with blood the risk of contracting hepatitis B from these fluids is practically nonexistent. Hepatitis B is not transmitted by casual contact. However the virus can spread through intimate contact with carriers in a household setting. Why this happens is not completely understood. Somehow the virus can find its way into the bloodstream of fellow family members possibly because of frequent physical contact with the small cuts or skin rashes. The virus can also spread through biting and possibly by the sharing of toothbrushes or razors. SymptomsIn mild cases the signs and symptoms are those of a minor infection. In severe cases they are extreme reactions resulting from liver failure. The extent of the illness depends on the original size of the dose of the virus the route of exposure and the specific response of the infected individual. More than half of hepatitis B infections occur and pass without noticeable symptoms. Sometimes only mild symptoms such as a general discomfort occur. Rarely is medical attention needed. Often the infection disappears without treatment. In fact laboratory testing is often the only way of determining whether someone has had hepatitis B. When symptoms develop the earliest ones often appear flu-like:
In a relatively few cases these symptoms are followed by jaundice causing skin to yellow and urine to darken--typical signs of a malfunctioning liver. An accumulation of a waste product called bilirubin in the blood causes this yellowish colour. Jaundice and other symptoms usually subside gradually within 3 to 4 weeks and most patients fully recover in the process becoming immune to the disease. People with serious cases of hepatitis B require hospitalization. A very small proportion of these patients develop a critical form of the disease called "fulminant" hepatitis B. This condition results from a sudden breakdown of liver function. Fulminant hepatitis B is extremely serious. TreatmentThere is no specific treatment for patients with hepatitis B although research is continuing. Physicians commonly recommend that patients with the disease limit their physical activity although they do not necessarily restrict them to bed-rest. They also advise patients to drink clear liquids during the early stages of the infection and to avoid high-protein diets and alcohol. To combat hepatitis B the body has several defenses. White blood cells which protect the body from infections attack and destroy the infected liver cells. The body also produces antibodies which circulate in the blood to destroy the virus and protect against future infections of hepatitis B. During the infection and recovery process the liver may not function normally causing illness that affects the entire body. Hospitalization may be required for patients who suffer from severe vomiting and who are unable to maintain adequate nutritional levels. It may also be required to prevent the development of complications. For reasons that are not completely understood 10 percent of people who develop hepatitis B become carriers of the disease. Their blood remains infected for months years sometimes for life. Seventy percent of carriers develop chronic persistent hepatitis B. Most do not appear to be ill. The remaining 30 percent of carriers experience continuous liver disease. This condition often progresses to cirrhosis and then after 30 to 40 years possibly to liver cancer. At present there is no way of curing carriers. PreventionTwo hepatitis B vaccines are licensed in Canada. Both provide safe reliable protection from hepatitis B when used either before or immediately after exposure to the virus. Tests show 90 to 95 percent of vaccinations of healthy people result in the development of resistance against hepatitis B. At present vaccination is the surest way to avoid acquiring hepatitis B. However it is also wise to avoid exposure to the virus. Because hepatitis B is more common in hospitals labs and other workplaces where people come into contact with blood and other body fluids infection control precautions are the first line of defense. These include frequent hand washing the wearing of gloves and the proper disposal of syringes and cleaning of medical instruments. Outside the workplace setting hepatitis B can be transmitted by sharing needles and during sexual intercourse. It is in fact one of the fastest-spreading sexually transmitted infections. You can protect yourself by:
Hepatitis B can also be picked up during body piercing or tattooing. Always ensure the artist uses a new needle straight out of the package. Additional Resources: |