HIV and Its Transmission
Research has revealed a great deal of valuable medical, scientific, and public health information about the human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS). The ways in which HIV can be transmitted have been clearly identified. Unfortunately, false information or statements that are not supported by scientific findings continue to be shared widely through the Internet or popular press. Therefore, the Centers for Disease Control and Prevention (CDC) has prepared this fact sheet to correct a few misperceptions about HIV.
How HIV Is Transmitted
HIV is spread by sexual contact with an infected person, by sharing needles (primarily for drug injection) with someone who is infected, or, less commonly, through transfusions of infected blood or blood clotting factors (凝血因子). Babies born to HIV-infected women may become infected before or during birth or through breast-feeding after birth.
Some people fear that HIV might be transmitted in other ways; however, no scientific evidence supporting any of these fears has been found. If HIV were being transmitted through other routes (such as through air, water, or insects), the pattern of reported AIDS cases would be much different from what has been observed. For example, if mosquitoes could transmit HIV infection, many more young children and preadolescents would have been diagnosed with AIDS.
All reported cases suggesting new or potentially unknown routes of transmission are thoroughly investigated by state and local health departments with the assistance, guidance, and laboratory support from CDC. No additional routes of transmission have been recorded, despite a national sentinel (监测) system designed to detect just such an occurrence.
The following paragraphs specifically address some of the common misperceptions about HIV transmission.
HIV in the Environment
Scientists and medical authorities agree that HIV does not survive well in the environment, making the possibility of environmental transmission remote. HIV is found in varying concentrations or amounts in blood, semen (精液), vaginal (阴道的) fluid, breast milk, saliva (唾液), and tears. To obtain data on the survival of HIV, laboratory studies have required the use of artificially high concentrations of laboratory-grown virus. Since the HIV concentrations used in laboratory studies are much higher than those actually found in blood or other specimens, drying of HIV-infected human blood or other body fluids reduces the theoretical risk of environmental transmission to that which has been observed—essentially zero. Incorrect interpretation of conclusions drawn from laboratory studies has unnecessarily alarmed some people.
Results from laboratory studies should not be used to assess specific personal risk of infection because: (1) The amount of virus studied is not found in human specimens or elsewhere in nature, and (2) no one has been identified as infected with HIV due to contact with an environmental surface. Additionally, HIV is unable to reproduce outside its living host except under laboratory conditions. Therefore, it does not spread or maintain infectiousness outside its host.
Households
Although HIV has been transmitted between family members in a household setting, this type of transmission is very rare. These transmissions are believed to have resulted from contact between skin or mucous membranes (黏膜) and infected blood. To prevent even such rare occurrences, precautions should be taken in all settings "including the home" to prevent exposure to the blood of persons who are HIV infected, at risk for HIV infection, or whose infection and risk status are unknown, For example.
Gloves should be worn during contact with blood or other body fluids that could possibly contain vis

A. Y
B. N
C. NG