أسبابه وكيفية إنتقاله:Hepatitis B infection is caused by the hepatitis B virus (HBV). HBV is passed from person to person through blood, semen or other body fluids. When HBV enters your liver, it invades the liver cells and begins to multiply. This causes inflammation in the liver and leads to the signs and symptoms of hepatitis B infection
The virus can survive outside the body for at least 7 days and still able to cause infection
Blood
Direct contact with infected blood can transmit the hepatitis B virus through:
punctures of the skin with blood-contaminated needles, lancets, scalpels, or other sharps
splashes to skin bearing minute scratches, abrasions, burns, or even minor rashes
splashes to mucous membranes in the mouth, nose, or eyes
To a lesser extent, indirect contact with blood-contaminated surfaces can also transmit the hepatitis B virus. The virus may be stable in dried blood for up to 7 days at 25?C. Hand contact with blood-contaminated surfaces such as laboratory benches, test tubes, or laboratory instruments may transfer the virus to skin or mucous membranes.
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 to workers is not known.
Feces, nasal secretions, sputum, sweat, tears, urine, and vomit have not been implicated in the spread of hepatitis B. Unless they are visibly contaminated with blood, the risk of contracting hepatitis B from these fluids in the workplace is practically nonexistent.
Hepatitis B is not transmitted by casual contact. For example, hospital employees who have no contact with blood, blood products, or blood-contaminated fluids are at no greater risk than the general public. 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. It is not spread through sneezing, coughing, hand holding, hugging, breastfeeding, sharing eating utensils, water or food.
What occupations have increased risk of hepatitis B?
The risk of acquiring hepatitis B from the workplace depends on the amount of exposure to:
human blood or blood products, or other body fluids and tissues known to transmit the hepatitis B virus
needlestick injuries or other puncture injuries from sharp instruments contaminated with blood
close contact with people who carry the hepatitis B virus in family or institutional residence settings
Blood tests show that certain occupational groups have different risks of getting hepatitis B.
table1
Risks to Occupational Groups
Percentage of people having evidence of past hepatitis B infection Occupational Group
High (over 20%) Pathologists, biochemistry and hematology laboratory personnel, dialysis staff
Intermediate (7-20%) Hospital nurses, laboratory personnel other than those in high risk groups, staff of institutions for the developmentally handicapped, dentists
Low (less than 7%) Administrative hospital staff, medical and dental students, healthy adults
In general, occupational groups with increased risk include:
health-care workers repeatedly exposed to blood or blood products or those who are at risk of needlestick injury
dentists, dental assistants, and dental hygienists
certain staff members of institutions for the developmentally handicapped
staff of institutions where workers may be exposed to aggressive, biting residents
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المصدر:
http://www.mayoclinic.com/health/hepatitis-b/DS00398/DSECTION=causeshttp://www.ccohs.ca/oshanswers/diseases/hepatitis_b.html