preparation of HIV that was completely inactivated in the laboratory might still be able to transmit infection in vivo.

The amount of both free HIV and virus-infected cells present in the blood of infected individuals varies with the stage of the infection (see Chapter 1). During the acute infection stage, newly infected persons have extremely high levels of HIV present in circulating peripheral blood cells and in the plasma. When a host antiviral immune response is generated, typically within 1 to 3 months of initial infection, the levels of infected cells and plasma virus fall dramatically. HIV replication continues throughout the asymptomatic phase of the disease, primarily within the lymphoid organs of infected persons. During this period, recirculating HIV-infected lymphocytes and cell-free virus can be detected in the peripheral bloodstream. As a result, HIV-infected injection drug users are likely to be able to transmit the virus to others by sharing injection equipment throughout the entire course of their infection. Increasing levels of HIV and HIV-infected cells appear in the blood of infected persons as immune containment of virus replication fails and clinical disease becomes manifest.

Although epidemiologic evidence obtained from studies of heterosexual and perinatal transmission of HIV infection suggests that individuals who are in the acute or advanced stages of HIV infection may be more infectious than those in the early stages of the infection, no information concerning this issue has been reported in injection drug users (see Chapter 1). It seems reasonable to expect, however, that not all HIV-positive injection drug users are equally infectious. From the perspective of disinfection strategies for needles and syringes, effective methods need to be able to inactivate the viral burden present in contaminating blood derived from even the most highly infectious individuals.

Although it is commonly assumed that HIV transmission among injection drug users results from sharing contaminated needles and syringes, there are a number of additional factors that may account for virus spread. For example, HIV contamination of other materials used by injection drug users, including the paraphernalia used to mix and prepare drugs for injection ("cookers") and the water used to dissolve the drugs or rinse the needles and syringes between their use by different individuals, can potentially serve to transmit HIV. The relative roles of these different materials and processes in spreading HIV among injection drug users are not known.

BLEACH AS A DISINFECTANT

Definition of Terms

Although the terms sterilization and disinfection are widely employed, they are often misused (Block, 1983). Sterilization is the use of physical or



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