Epidemiologic Notes and Reports

 April 22, 1988 / 37(15);229-234

AIDS and HIV Update: Acquired Immunodeficiency Syndrome and Human Immunodeficiency Virus Infection Among Health-Care Workers

Acquired immunodeficiency syndrome (AIDS) among health-care workers in the United States results primarily from human immunodeficiency virus (HIV) infections that occur outside of the health-care setting. However, a small number of health-care workers have been infected with HIV through occupational exposures, and one such worker has developed AIDS after documented seroconversion. This report summarizes and updates both national surveillance data for AIDS among health-care workers and data from prospective studies on the risk of HIV transmission in the health-care setting.

Health-Care Workers with AIDS

The AIDS case report form used by CDC requests that state and local health departments collect information on employment since 1978 in a health-care or clinical laboratory setting. For surveillance purposes, any person who indicates such employment is classified as a health-care worker.

As of March 14, 1988, a total of 55,315 adults with AIDS had been reported to CDC. Occupational information was available for 47,532 of these persons, 2,586 (5.4%) of whom were classified as health-care workers. A similar proportion (5.7%) of the U.S. labor force was employed in health services (1).

Forty-six states, the District of Columbia, and Puerto Rico have reported health- care workers with AIDS. Like other AIDS patients, health-care workers with AIDS had a median age of 35 years. Males accounted for 91.6% of health-care workers with AIDS and 92.4% of other patients with AIDS. The majority of health-care workers with AIDS (62.8%) and of other AIDS patients (60.5%) were white.

Ninety-five percent of the health-care workers with AIDS were classified into known transmission categories (Table 1). Health-care workers with AIDS were significantly less likely than others with AIDS to be intravenous drug abusers and more likely to be homosexual or bisexual men. They were also less likely to have a known risk factor reported (p less than 0.001).

To determine the possible cause of HIV infection, state and local health departments investigate those AIDS patients reported as having no identified risk. As of March 14, 1988, investigations had been completed for 121 of the 215 health-care workers initially reported with undetermined risk. Risk factors were identified for 80 (66.1%) of these. Of the 135 health-care workers who remain in the undetermined-risk category, 41 (30.4%) could not be reclassified after follow-up; 20 (14.8%) had either died or refused to be interviewed; and 74 (54.8%) are still under investigation.

Overall, 5.3% of health-care workers with AIDS had an undetermined risk. When examined by year of report to CDC, the proportion of such health-care workers appears to have increased from 1.5% in 1982 to 6.2% in 1987. However, 71 of the 135 health-care workers for whom risk is still undetermined have been reported since March 1987, and 80.0% of these 71 cases are still under investigation. The proportion of other AIDS patients with an undetermined risk has also increased over time. However, previous experience suggests that other risk factors for HIV infection will be identified for many of these persons when investigations have been completed (2). Ten percent of all reported AIDS patients with undetermined risk are health-care workers; this proportion has not changed over time.

A health-care worker reported to have developed AIDS after a well-documented occupational exposure to blood and HIV seroconversion is included among the 80 health-care workers who were reclassified after follow-up. The worker was accidentally self-injected with several milliliters of blood from a hospitalized patient with AIDS while filling a vacuum collection tube. Investigation revealed no other risk factors for this health-care worker.

Forty-one health-care workers could not be reclassified after investigation; 68.3% were men. In contrast, 23.0% of individuals employed in hospitals and health services in the United States are men (1). These 41 health-care workers comprised eight physicians, four of whom were surgeons; one dentist; five nurses; eleven nursing assistants or orderlies; seven housekeeping or maintenance workers; four clinical laboratory technicians; one respiratory therapist; one paramedic; one mortician; and two others who had no contact with patients or clinical specimens. A comparison of the occupations of these 41 health-care workers with those of health-care workers for whom risk factors and job information were available showed that maintenance workers were the only occupational group significantly more likely to have an undetermined risk (7 (17.1%) of 41 health-care workers with undetermined risk, compared with 160 (7.1%) of 2,263 health-care workers with identified risk, p = 0.02).

Seventeen of the 41 investigated health-care workers with undetermined risk (including two of the seven maintenance workers) reported needlestick and/or mucous-membrane exposures to the blood or body fluids of patients during the 10 years preceding their diagnosis of AIDS. However, none of the patients was known to be infected with HIV at the time of exposure, and none of the health-care workers was evaluated at the time of exposure to document seroconversion to HIV antibody. None of the remaining 24 health-care workers reported needlestick or other nonparenteral exposures to blood or body fluids.

Other Health-Care and Laboratory Workers with HIV Infection

As of December 31, 1987, 1,176 health-care workers had been enrolled and tested for HIV antibody in ongoing CDC surveillance of health-care workers exposed to blood or other body fluids from HIV-infected patients. Of the 1,070 workers tested greater than or equal to90 days after exposure, 870 (81.3%) had parenteral exposures to blood; 104 (9.7%) had exposures of mucous membrane or nonintact skin to blood; and 96 (9.0%) had exposures to other body fluids (Table 2).

Four (0.5%) of the 870 workers with parenteral exposures to blood were seropositive for HIV antibody (upper bound of the 95% confidence interval (CI) = 1.1%). However, one of these four was not tested until 10 months after exposure (3,4). In addition, this worker had an HIV-seropositive sexual partner, and heterosexual acquisition of infection could not be excluded. Of the 489 health-care workers who sustained parenteral exposures to blood and for whom both acute- and convalescent- phase serum samples had been obtained, three, or 0.6%, seroconverted to HIV within 6 months of exposure (upper bound of the 95% CI = 1.6%) (4-6). Investigation revealed no nonoccupational risk factors for these three workers.

Two other ongoing prospective studies assess the risk of nosocomial acquisition of HIV infection among health-care workers in the United States (7,8). As of April 30, 1987, the National Institutes of Health had tested 103 health-care workers with documented needlestick injuries and 691 health-care workers with more than 2,000 cutaneous or mucous-membrane exposures to blood or other body fluids of HIV-infected patients; none had seroconverted (7). As of March 15, 1988, a similar study at the University of California of 235 health-care workers with 644 documented needlestick injuries or mucous-membrane exposures had identified one seroconversion following a needlestick (9; University of California, San Francisco, unpublished data). Prospective studies in the United Kingdom and Canada show no evidence of HIV transmission among 220 health-care workers with parenteral, mucous- membrane, or cutaneous exposures (10,11).

In addition to the health-care workers enrolled in these longitudinal surveillance studies and the case reported here, six persons from the United States and four persons from other countries who denied other risk factors for HIV infection have reportedly seroconverted to HIV after parenteral, nonintact skin, or mucous- membrane exposures to HIV-infected blood or concentrated virus in a health-care or laboratory setting (Table 3) (12-20). Six additional health-care workers with no other identified risk factors reportedly acquired HIV infection, but the date of seroconversion is unknown (3,15,21-23). Reported by: AIDS Program, Hospital Infections Program, Center for Infectious Diseases, CDC. Editorial Note: These data are consistent with previous observations that the occupational risk of acquiring HIV in health-care settings is low and is most often associated with percutaneous inoculation of blood from a patient with HIV infection. Prospective surveillance studies, which provide data on the magnitude of the risk of HIV infection, indicate that the risk of seroconversion following needlestick exposures to blood from HIV-infected patients is less than 1.0%. The level of risk associated with the exposure of nonintact skin or mucous membranes is likely far less than that associated with needlestick exposures. Individual published case reports must be interpreted with caution because they provide no data on the frequency of occupational exposures to HIV or the proportion of exposures resulting in seroconversion.

The reasons that a higher proportion of health-care workers with AIDS have no identified risk than do other persons with AIDS are unknown. They could include a tendency of health-care workers not to report behavioral risk factors for HIV infection, the occupational risk of HIV infection as a result of blood exposure, or both. The first hypothesis is suggested by the overrepresentation of men among these health-care workers, a finding that is similar to the overrepresentation of men among AIDS patients infected with HIV through sexual activity or intravenous drug abuse. The second hypothesis is suggested by the documentation of HIV

 transmission in the health-care setting. Similar hypotheses may be raised for the apparent excess of maintenance personnel among health-care workers with no identified risk for AIDS. Occupationally acquired HIV infection in such workers would be difficult to determine unless the source patient or clinical specimen was known to be HIV-positive, the occupational exposure had been well documented, and the HIV seroconversion of the health-care worker had been detected.

The increasing number of persons being treated for HIV-associated illnesses makes it likely that more health-care workers will encounter patients infected with HIV. The risk of transmission of HIV can be minimized if health-care workers use care while performing all invasive procedures, adhere rigorously to previously published recommendations, and use universal precautions when caring for all patients (5). In addition, employers should instruct health-care workers on the need for routine use of universal precautions, provide equipment and clothing necessary to minimize the risk of infection, and monitor workers' adherence to these precautions (5,24). References

1.      Bureau of Labor Statistics. Employment and earnings. Washington, DC: US Department of Labor, Bureau of Labor Statistics, 1988;35:13,93,194.

2.      Castro KG, Lifson AR, White CR, et al. Investigations of AIDS patients with no previously identified risk factors. JAMA 1988;259:1338-42.

3.      Weiss SH, Saxinger WC, Rechtman D, et al. HTLV-III infection among health care workers: association with needle-stick injuries. JAMA 1985;254:2089-93.

4.      McCray E, The Cooperative Needlestick Surveillance Group. Occupational risk of the acquired immunodeficiency syndrome among health care workers. N Engl J Med 1986; 314:1127-32.

5.      Centers for Disease Control. Recommendations for prevention of HIV transmission in health-care settings. MMWR 1987;36(suppl 2S).

6.      Stricof RL, Morse DL. HTLV-III/LAV seroconversion following a deep intramuscular needle- stick injury (Letter). N Engl J Med 1986;314:1115.

7.      Henderson DK, Saah AJ, Fahey BJ, Schmitt JM, Lane HC. Prospective assessment of the risk for occupational/nosocomial infection with human immunodeficiency virus in a large cohort of health care workers (Abstract no. 76). In: Program and abstracts of the Twenty-Seventh Interscience Conference on Antimicrobial Agents and Chemotherapy. Washington, DC: American Society for Microbiology, 1987:109.

8.      Gerberding JL, Bryant-LeBlanc CE, Nelson K, et al. Risk of transmitting the human immunodeficiency virus, cytomegalovirus, and hepatitis B virus to health care workers exposed to patients with AIDS and AIDS-related conditions. J Infect Dis 1987;156:1-8.

9.      Gerberding JL, Henderson DK. Design of rational infection control policies for human immunodeficiency virus infection. J Infect Dis 1987;156:861-4.

10. McEvoy M, Porter K, Mortimer P, Simmons N, Shanson D. Prospective study of clinical, laboratory, and ancillary staff with accidental exposures to blood or body fluids from patients infected with HIV. Br Med J 1987;294:1595-7.

11. Health and Welfare Canada. National surveillance program on occupational exposure to HIV among health-care workers in Canada. Canada Dis Weekly Rep 1987;13-37:163-6.

12. Anonymous. Needlestick transmission of HTLV-III from a patient infected in Africa. Lancet 1984;2:1376-7.

13. Oksenhendler E, Harzic M, Le Roux JM, Rabian C, Clauvel JP. HIV infection with seroconversion after a superficial needlestick injury to the finger (Letter). N Engl J Med 1986; 315:582.

14. Neisson-Vernant C, Arfi S, Mathez D, Leibowitch J, Monplaisir N. Needlestick HIV seroconversion in a nurse (Letter). Lancet 1986;2:814.

15. Weiss SH, Goedert JJ, Gartner S, et al. Risk of human immunodeficiency virus (HIV-1) infection among laboratory workers. Science 1988;239:68-71.

16. Centers for Disease Control. 1988 agent summary statement for human immunodeficiency virus and report on laboratory-acquired infection with human immunodeficiency virus. MMWR 1988;37(suppl S-4).

17. Centers for Disease Control. Apparent transmission of human T-lymphotrophic virus type III/lymphadenopathy-associated virus from a child to a mother providing health care. MMWR 1986;35:76-9.

18. Centers for Disease Control. Update: human immunodeficiency virus infections in health- care workers exposed to blood of infected patients. MMWR 1987;36:285-9.

19. Ramsey KM, Smith EN, Reinarz JA. Prospective evaluation of 44 health care workers exposed to human immunodeficiency virus-1, with one seroconversion (Abstract). Clin Res 1988;36:1A.

20. Gioannini P, Sinicco A, Cariti G, Lucchini A, Paggi G, Giachino O. HIV infection acquired by a nurse. Eur J Epidemiol 1988;4:119-20.

21. Grint P, McEvoy M. Two associated cases of the acquired immune deficiency syndrome (AIDS). PHLS Commun Dis Rep 1985;42:4.

22. Klein RS, Phelan JA, Freeman K, et al. Low occupational risk of human immunodeficiency virus infection among dental professionals. N Engl J Med 1988;318:86-90.

23. Ponce de Leon RS, Sanchez-Mejorada G, Zaidi-Jacobson M. AIDS in a blood bank technician in Mexico City (Letter). Infect Control Hosp Epidemiol 1988;9:101-2.

24. US Department of Labor, US Department of Health and Human Services. Joint Advisory Notice: protection against occupational exposure to hepatitis B virus (HBV) and human immunodeficiency virus (HIV). Federal Register 1987;52:41818-24.