AIDS: are laboratorians at risk?

As of this writing, there has not been a single documented case of AIDS transmission to a U.S. health care worker through occupational exposure.

The possibility of this happening is remote, on the basis of all available evidence. Nevertheless, laboratory personnel, nurses, physicians and others in health care are apt to worry whenever they read or thear that someone in their job category has come down with AIDS. If the headlines are often scary, the full story is, in my opinion, reassuring.

Let's look first at the 278 AIDS cases reported among U.S. health care workers as of Feb. 11. According to the Centers for Disease Control, all but 24 (9 per cent) belonged to population groups known to be at risk for AIDS.

Epidemiological investigations were completed in 17 of the 24 cases not linked to groups at risk. In six, nonoccupational exposures were deemed the most likely source of infection. How AIDS develop d in the other 11 health care workers remains a mystery, but specific occupational exposure to a definite or suspected AIDS patient could not be documented. Four more of the 2j cases are still under epidemiological investigation; death occurred before investigations were completed in three cases.

Fifty-six of the AIDS cases involved clinical laboratory technologists and technicians. All but three belonged to groups at risk. One well-publicized case involved an employee at a Boston independent laboratory who died Jan. 12, two months after being hospitalized. He had told doctors that he recalled at least one accidental needlestick while drawing blood from a patient. Although this was not absolutely ruled out as the cause of his infection, investigators failed to uncover any AIDS patients he had dealt with.

An epidemiologist who studied that case says: "All possibilities are open. But I am not convinced that this represents the first case of AIDS due to direct contact with a patient."

The CDC maintains surveillance of health care workers exposed to potentially infectious body fluids from definite or suspected AIDS patients. As of the beginning of this year, 361 health care workers were enrolled in the surveillance registry, and none has developed AIDS symptoms.

Now it is true that a nurse in a British hospital tested positive for HTLV-III antibody within two months of a needlestick injury involving an AIDS patient. A report in the Dec. 15, 1984, Lancet noted that the nurse had been "resheathing a hypodermic needle on a syringe containing fresh blood drawn from an arterial line. This was not an ordinary needlestick injury, in that a small amount of blood may have been injected."

Dr. George F. Grady, epidemiologist for the Massachusetts Department of Health, calls the British case "a flagrant exposure." It may be theoretically possible to contract AIDS through on-the-job contact, but he says it would be an extremely rare occurrence, "probably much rarer than hepatitis, because the efficiency of transmission appears to be less."

Finally, Martin S. Hirsch, M.D., et al, published a paper on the risk of nosocomial infection with human T-cell lymphotropic virus III (HTLV-III), in the Jan. 3, 1985, issue of the New England Journal of Medicine. The researchers studied the HTLV-III serologic status of 85 employees at a Boston hospital and a Valhalla, N.Y., hospital who had needlestick inoculations or repeated exposures to specimens from AIDS patients over a three-year period.

Thirty of the hospital employees suffered needlestick accidents, another reported that her s eye was splattered with blood from an AIDS patient, and two others had blood contamination of an open hand wound. Laboratorians who worked with blood specimens and eight pathologists who had processed biopsy specimens from AIDS patients were also part of the study group.

None of the 85 employees with nosocomial exposure to specimens from AIDS patients tested positive for HTLV-III antibody.

The researchers concluded: "Our results...suggest that the isolation procedures currently recommended for AIDS are adequate and that the risk of transmission within hospitals is low. Moreover, accidental needlestick exposure appears to provide little additional risk of transmission."