Frequent opportunities for unrecognized direct contact with contaminated materials and surfaces were reported to be present. Gloves of questionable integrity, skin cuts and abrasions, and one episode of a dermatitis-like condition represented portals for possible exposure and routes of infection. The most probable cause for the second worker's infection was parenteral inoculation. This worker recalled incurring an injury with a blunt cannula approximately 6 months before the first seropositive sample. Incidents of contamination, such as those reported by the first worker, occurred infrequently in the second worker's laboratory.
Aerosol transmission is considered to be the least likely cause of infection in both cases.
Operations in which aerosols may have been generated were carried out in biological safety cabinets to reduce the potential for inhalation exposure. The occupational risk for infection by parenteral exposure is substantially reduced or eliminated by strict adherence to BSL 2 practices. The recommended use of BSL 3 practices for highly concentrated preparations of HIV is appropriate. There is a need, however, for more proficiency and discipline in laboratory safety practices. The most important recommendation is to adhere strictly to standard microbiologic practices and techniques.