ABC of Safety in the Biological Sciences




A.I.D.S.(Acquired immune deficiency syndrome)

AIDS is a disease in which the immune system of the body is damaged through infection by the Human Immunodeficiency Virus (HIV). This results in susceptibility to a variety of infective agents and some unusual forms of neoplasia.22 The emergence of AIDS as a significant transmissible disease has implications for all medical laboratory personnel and a number of cases of seroconversion in laboratory workers have been reported.23 24 The AIDS virus may be transmitted by the percutaneous inoculation of blood, semen or other body fluid.

Extraordinary precautions of containment are not required to protect laboratory personnel against infection by HIV. Special procedures should not need to be introduced for HIV-positive blood or other specimens nor is there a need for these specimens to be handled separately in the laboratory.25 The most effective means of preventing infection in laboratory workers is to assume that all specimens are potentially infectious. Gloves and gowns should be worn by persons in contact with blood, blood specimens, serum, tissue or any body fluid or excretion. Wash hands thoroughly after dealing with any specimen. It is not necessary to routinely wear a mask6 and eye protection need only be worn where splattering may occur. In the event of a splash, bathe or rinse the exposed tissue or membrane gently with water to minimise the risk of infection.

Needles and syringes should be disposed of in rigid wall, puncture resistant containers. Should a needle puncture occur report the injury immediately to the infectious control authority so that appropriate treatment can be obtained.

Disinfecting Agents suitable for HIV

Formalin, 0.5% diluted in distilled water (40% formaldehyde, laboratory grade, is regarded as being 100% formalin) inactivates the free virus in solution. 10% neutral buffered formalin, used for tissue fixation will inactivate the virus provided that the formalin has penetrated the tissue completely. However, formalin penetrates slowly and it may take several days to reach the centre of a large specimen.

A freshly prepared 2% aqueous solution of glutaraldehyde (laboratory grade) inactivates the virus and can be used for tissue fixation as well as for disinfecting instruments and benches. If glutaraldehyde is used as a disinfectant apply liberally. Contact with the virus is required for at least 60 minutes.

Technical Note: Glutaraldehyde vapour is toxic and so care should be taken when using the substance in an open area.

Sodium hypochlorite
Sodium hypochlorite, laboratory grade, prepared as a 0.5% solution in distilled water, is suitable as a disinfectant for porous surfaces, benches, floors and walls and spills of any sort, or heavily contaminated surfaces. If sodium hypochlorite is used as a disinfectant contact with virus is required for at least 30 minutes.

Technical Note: Higher concentrations of sodium hypochlorite can be used for shorter periods. However, sodium hypochlorite in solutions of higher concentrations is corrosive.

Ethanol, laboratory grade, diluted to 70% with distilled water, is an acceptable disinfectant if allowed to remain in contact with the virus for 60 minutes. Repeated contacts may be required because of the volatility of ethanol.

Autopsy and Mortuary Procedures These are similar to procedures applied in other infectious diseases.26 The number of personnel in attendance at the autopsy should be kept to a minimum. Gowns, plastic aprons, gloves and boots must be worn. The greatest risk occurs during embalming and when decontaminating infected material, such as body fluids and faeces, before disposal.



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