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  3. HIV and Its Transmission Research has revealed a great deal of valuable medical, scientific, and public health information a

HIV and Its Transmission Research has revealed a great deal of valuable medical, scientific, and public health information a

admin2010-04-12  67
问题                           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 visible blood, such as urine, feces (粪便), or vomit.
    Cuts, sores, or breaks on both the caregiver’s and patient’s exposed skin should be covered with bandages.
    Hands and other parts of the body should be washed immediately after contact with blood or other body fluids, and surfaces soiled with blood should be disinfected appropriately.
    Practices that increase the likelihood of blood contact, such as sharing of razors and toothbrushes, should be avoided.
    Businesses and Other Settings
    There is no known risk of HIV transmission to co-workers, clients, or consumers from contact in settings such as food-service establishments (see information on survival of HIV in the environment). Food-service workers known to be infected with HIV need not be restricted from work unless they have other infections or illnesses for which any food-service worker, regardless of HIV infection status, should be restricted. CDC recommends that all food-service workers follow recommended standards and practices of good personal hygiene and food sanitation.
    Kissing
    Casual contact through closed-mouth or "social" kissing is not a risk for transmission of HIV. Because of the potential for contact with blood during "French" or open-mouth kissing, CDC recommends against engaging in this activity with a person known to be infected. However, the risk of acquiring HIV during open-mouth kissing is believed to be very low. CDC has investigated only one case of HIV infection that may be attributed to contact with blood during open-mouth kissing.
    Saliva, Tears, and Sweat
    HIV has been found in saliva and tears in very low quantities from some AIDS patients. It is important to understand that finding a small amount of HIV in a body fluid does not necessarily mean that HIV can be transmitted by that body fluid. HIV has not been discovered from the sweat of HIV-infected persons. Contact with saliva, tears, or sweat has never been shown to result in transmission of HIV.
    Insects
    From the onset of the HIV epidemic, there has been concern about transmission of the virus by biting and bloodsucking insects. However, studies conducted by researchers at CDC and elsewhere have shown no evidence of HIV transmission through insects—even in areas where there are many cases of AIDS and large populations of insects such as mosquitoes. Lack of such outbreaks, despite intense efforts to detect them, supports the conclusion that HIV is not transmitted by insects.
    The results of experiments and observations of insect biting behaviour indicate that when an insect bites a person, it does not inject the blood of its own or a previously bitten person or animal into the next person bitten. Such diseases as yellow fever and malaria (疟疾) are transmitted through the saliva of specific species of mosquitoes. However, H1V lives for only a short time inside an insect and, unlike organisms that are transmitted via insect bites, HIV does not reproduce (and does not survive) in insects. Thus, even if the virus enters a mosquito or other sucking or biting insect, the insect does not become infected and cannot transmit HIV to the next human it feeds on or bites.
The writer tells us there are three routes of transmitting HIV.
选项 A、Y
B、N
C、NG
答案B
解析
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