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Health care workers and the risk of HIV transmission.

Health Care Workers and the Risk of HIV Transmission

In the last decade, tens of thousands of persons with acquired immunodeficiency syndrome (AIDS) have been treated in the health care system in the United States. Hundreds of thousands more infected with human immunodeficiency virus (HIV) but often not identified as such have also received medical, dental and nursing services. Although isolated cases of HIV infection in health care personnel have created a high level of anxiety about the risk of treating such patients, the actual probability of contracting infection is extremely small.

The first descriptions of persons with the disease now known as AIDS were reported to the Centers for Disease Control (CDC) in the spring of 1981. [1] It was not until the fall of 1982, however, when more than 600 cases had been reported, that cumulative epidemiologic data strongly suggested that AIDS was caused by a transmissible (infectious) agent. In response CDC published the first recommended precautions for clinical and laboratory personnel working with persons with AIDS or associated conditions (specified as chronic, generalized lymphadenopathy, unexplained weight loss, and/or prolonged unexplained fever in persons at risk for AIDS). [2] This report noted that at that time there was "no evidence of AIDS transmission to hospital personnel from contact with affected patients or clinical specimens." The patterns of transmission for the unknown agent that caused AIDS appeared similar to those of hepatitis B virus (HBV), however, and hospital personnel were advised to use the same precautions when providing care for a person with AIDS as for those with HBV.

To document the risk of infection to health care workers, several prospective studies were initiated in which personnel working with patients with AIDS or who had been inadvertently exposed to blood or other body fluids of patients were evaluated for evidence of illness. Once HIV was identified as the cause of AIDS and serologic tests for determining antibody status became available in 1985, these studies had a more rapid and sensitive marker to confirm infection acquired in the workplace. These studies and anecdotal reports published over the last four years have documented that HIV can be transmitted to health care workers, although such occurrences are extremely infrequent. Virtually all confirmed infections occurred after an accidental injury, most often by injury from a needle that had been used on a patient.

In May 1987, however, a report documented HIV infection in three health care workers who had been exposed to blood from a person with HIV infection only on their skin or mucous membranes. [3] The anxiety engendered by this report has been unmistakable, and has given rise not only to broadened recommendations to try to prevent this type of exposure, [4] but also to inappropriate suggestions for management of persons with AIDS or HIV infection in health care settings.

If there were a significantly increased risk of AIDS to health care workers because of occupational exposure, one would expect a higher percentage of persons with AIDS to be employed in health care when compared with other professions. Almost 50,000 adults in the United States had been diagnosed with AIDS and reported to the CDC through December 1987. Selected information about employment is available for approximately 86 percent of the first 40,000 cases.

* In cases with known employment information, 2,232 (5.6%) reported employment in a health care setting before or at the time of diagnosis.

* Almost precisely the same proportion of persons in the total labor force are reported to be employed in health services. [5]

The age, race, and sex distribution of persons with AIDS employed in health services is similar to that of all AIDS cases. Most (95.1%) have a risk factor for HIV infection unrelated to employment. Persons with AIDS who are initially reported not to have a risk factor for infection are investigated intensively by state or local health departments to determine a probable means of HIV infection. Investigations have been completed on more than half the health care workers who initially did not have an identified risk for HIV infection and approximately 65 percent had a risk factor unrelated to employment; most cases with incomplete investigations were reported within the last twelve months.

Of the 108 health care workers currently classified as having no known risk for HIV infection, 17 percent have died or have refused to be interviewed, while 50 percent of the cases are still under review. Investigations of only thirty-six persons (33%) have been completed without resolution of the probable means of exposure to HIV. These include physicians and surgeons, dentists or dental personnel, nurses or nursing assistants, laboratory technicians, therapists, housekeeping and maintenance workers, and several others (such as administrative personnel) who had no contact with patients. Although there is heightened concern on the part of professionals in surgical specialties, in these studies the distribution of the specific occupations of health care workers with a well-defined risk of HIV infection were similar to those without an identified risk with the exception of service workers (including housekeeping and maintenance workers), who were more likely not to have an identified risk.

It is possible that one or more of these thirty-six health care workers acquired HIV infection in the workplace. Although sixteen did recall parenteral or other types of exposures to blood or fluids from patients during the decade preceeding their illness, none recalled specific exposure to potentially infectious materials from a person with AIDS or known HIV infection and none had been tested for antibody prior to suspected exposure.

Seven studies have examined the risk of HIV infection in health care personnel working with or exposed to potentially infectious blood or body fluids. All the studies have demonstrated that the risk of infection, even after accidental injury, is extremely low.

CDC is coordinating a cooperative multihospital study in which personnel with accidental exposure to blood, serum, or other potentially infectious fluids are assessed for risk of infection.

* Of the first 451 personnel evaluated, only two (0.44%) were seropositive after exposure. [6]

* In a subsequent analysis of 883 health care workers enrolled in the study as of June 30, 1987, only four (0.54%) became seropositive after exposure. [7] Three of these individuals were known to have seroconverted after exposure, and one person, for whom sexual transmission could not be excluded was first tested and found seropositive nine months after exposure.

Approximately 80 percent of the enrolled personnel had had percutaneous exposure to blood from a person with AIDS or HIV infection; the remainder were exposed through contamination of their mucous membranes or an open wound. The three persons who seroconverted in this study were among 351 (0.85%) who had percutaneous exposures and no other risk of HIV infection; none of the seventy-four personnel with exposure to skin or mucous membranes seroconverted.

* A study of 531 health care workers in a large research hospital found that 150 experienced some type of accidental exposure; none had serologic or other evidence of HIV infection during follow-up. [8]

* In a similar study in San Francisco, none of the 129 health care workers with needlestick injuries or mucous membrane exposures to blood or other potentially infectious fluids became infected after the exposure. [9] (Since publication of the initial results of this study, one person who was subsequently exposed and enrolled has seroconverted.)

* Another study of eighty-five health care workers with accidental exposure to infected blood or secretions or who were otherwise at risk of exposure (e.g., pathologists performing autopsies, physicians and nurses performing endoscopy) found none infected with HIV. [10]

* A prospective study of 246 female health care workers at a medical center in Los Angeles also found no seroconversions in the group, 102 of whom were classified as at high risk of exposure based on having handled specimens or worked with infected patients fifty or more times (mean, 354 contacts) during the preceding three years. [11] Ten workers reported needlestick exposures and fifteen mucous membrane exposures.

* In a final study, one (2.4%) of forty-two workers with accidental parenteral exposure to infected blood or serum and one (0.3%) of 294 health care workers without parenteral exposure were seropositive. [12] The study did not unequivocally rule out other sources of infection, and the time of seroconversion for both workers is unknown.

Risk of HIV infection has been assessed in a single cross-sectional study of 1,309 dental professionals (1,132 dentists, 131 hygienists, and 46 assistants). [13]

* Approximately 47 percent practiced in a geographic area with a high incidence of AIDS; 15 percent reported having treated persons with AIDS; and 72 percent had treated persons at risk of HIV infection.

Almost all (94%) reported one or more accidental injuries with sharp instruments in the preceeding five years. One dentist who had no other risk factors for HIV infection was seropositive; he had treated persons at risk for HIV infection but used barrier precautions only intermittently.

In addition to these studies, cases continue to be reported of other health care workers who have developed HIV infection (seroconversion) after accidental injury with exposure to blood or other body fluids from a patient with AIDS or HIV infection. In three cases, infection followed needlestick injury; one injury involved parenteral inoculation of blood, and two were reportedly relatively minor or superficial injuries. [14]

Two persons apparently became infected while providing nursing care to a person with AIDS or HIV infection. A mother who provided nursing care for her infant, who was hospitalized because of congenital problems and had become infected through a blood transfusion, did not follow barrier precautions (gloves) as she took care of her child. [15] Although the mother could recall no specific accidental exposure, she did have frequent contact with her child's blood and other body fluids. In the second case, a woman in England with no other known risk for HIV infection developed AIDS after providing home nursing care for a man diagnosed postmortem as having AIDS. [16] This woman also could not remember any specific accidental exposure, but she did not wear gloves while providing care and had repeated exposure to the patient's excretions and secretions.

Three additional cases involved health care workers whose skin came in direct contact with blood from HIV-infected patients, although none had direct parenteral inoculation of blood. [17] The exact means of infection in these cases is not known, but all three workers had skin lesions that could have provided a means of direct exposure. Only one of these persons was using barrier precautions at the time of exposure; the tube of blood she was filling splattered on her face and in her mouth.

The combined studies of almost 1,400 health care workers and 1,300 dental personnel suggest that the risk of HIV infection even after mucous membrane exposure or parenteral inoculation of infected blood, fluids, or secretions is extremely low--probably less than one per 200 incidents. This risk is probably a maximum estimate, since the denominator was selected only from those persons who had sustained one or more direct accidental exposures to potentially infectious blood or other fluids. If the actual risk of HIV transmission in medical, dental and nursing settings were higher than has been estimated in the published studies, it is almost certain that the number of AIDS cases in health care workers with no other identified risk would be considerably higher than has been observed.

The risk of seroconversion after an accidental parenteral injury or inoculation of blood may be associated with a number of variables, including the size of the inoculum. An experimental study suggested that the average volume of blood injected during a needlestick injury is only 1.4 microliters. [18] Several of the reports of health care workers who seroconverted after parenteral injury, however, indicated that the injury was not just a needlestick but involved the injection of blood. Under rare circumstances, HIV apparently can be transmitted without parenteral injury, presumbaly through minor injuries or abrasions on uncovered skin. The risk from this type of exposure has not been adequately quantified sine it is difficult to obtain reliable figures abou the frequency of this type of incident. Most experts estimate that the frequency was relatively common prior to the August 1987 recommendations to manage all patients in health care settings with universally applied blood and body fluid precautions. [19]

It is important to compare the observed risks to health care workers of HIV infection with the 6 percent to 30 percent risk of acquiring HBV infection after parenteral exposure to the blood of HBV infected patients. [20] In addition, the study of dental personnel noted that 21 percent of the personnel who had not been vaccinated against HBV had serologic evidence of past HBV infection. [21]

Many potentially dangerous exposures can be avoided if recommended infection control guidelines are followed. Although the risk of HIV transmission in the health care setting is already low, it can be reduced even further if health care personnel are meticulous in following such guidelines and in avoiding accidental injuries with needles and other sharp instruments. [22]


[1] Centers for Disease Control, "Pneumocystis pneumonia--Los Angeles," Morbidity and Mortality Weekly Report 30:21 (June 5, 1981), 250-52.

[2] Centers for Disease Control, "Acquired Immune Deficiency Syndrome (AIDS): Precautions for Clinical and Laboratory Staffs," Morbidity and Mortality Weekly Report 31:43 (November 5, 1982), 577-80.

[3] Centers for Disease Control, "Update: Human Immunodeficiency Virus Infection in Health-Care Workers Exposed to Blood of Infected Patients," Morbidity and Mortality Weekly Report 36:19 (May 22, 1987), 285-89.

[4] Centers for Disease Control, "Recommendations for Prevention of HIV Transmission in Health-Care Settings," Morbidity and Mortality Weekly Report 36:2S (Supplement)(August 21, 1987), 1S-18S.

[5] Centers for Disease Control, "Recommendations for Prevention of HIV Transmission in Health-Care Settings"; Alan R. Lifson, Kenneth G. Castro, Eugene McCray, and Harold W. Jaffe, "National Surveillance of AIDS in Health-Care Workers," Journal of the American Medical Association 256:23 (December 19, 1986), 3231-34.

[6] Eugene McCray and The Cooperative Needlestick Surveillance Group, "Occupational Risk of the Acquired Immunodeficiency Syndrome among Health-Care Workers," New England Journal of Medicine 314:17 (April 24, 1986), 1127-32.

[7] Centers for Disease Control, "Recommendations for Prevention of HIV Transmission in Health-Care Settings."

[8] Donald K. Henderson, Al J. Saah, B.S.N. Zak, et al., "Risk of Nosocomial Infection with Human T-Cell Lymphotropic Virus Type III/Lymphadenopathy-Associated Virus in a Large Cohort of Intensively Exposed Health-Care Workers," Annals of Internal Medicine 104:5 (May 1986), 644-47.

[9] J. Louise Gerberding, Charyl E. Bryant-LeBlanc, Kathleen Nelson, 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," Journal of Infectious Diseases 156:1 (July 1987), 1-8.

[10] Martin S. Hirsch, Gary P. Wormser, R. T. Schooley, et al., "Risk of Nosocomial Infection with Human T-Cell Lymphotropic Virus Type III (HTLV-III); New England Journal of Medicine 312:1 (January 3, 1985), 1-4.

[11] Thomas L. Kuhls, Susan Viker, Nancy B. Parris, et al., "Occupational Risk of HIV, HBV and HSV-2 Infections in Health Care Personnel Caring for AIDS Patietns," American Journal of Public Health 77:10 (October 1987), 1306-1309.

[12] Stanley H. Weiss, W. Carl Saxinger, D. Rechtman, et al., "HTLV-III Infection among Health-Care Workers: Association with Needle-Stick Injuries," Journal of the American Medical Association 254:15 (October 18, 1985), 2089-93.

[13] Robert S. Klein, Joan A. Phelan, Katherine Freeman, et al., "Los Occupational Risk of Human Immunodeficiency Virus Infection among Dental Professionals," New England Journal of Medicine 318:2 (January 14, 1988), 86-90.

[14] "Needlestick Transmission of HTLV-III from a Patient Infected in Africa," Lancet 2 (December 15, 1984), 1376-77; C. Neisson-Vernant, S. Arfi, D. Mathez, et al., "Needlestick HIV Seroconversion in a Nurse," Lancet 2 (April 5, 1986), 814; E. Oksenhendler, M. Harzic, J-M. Le Roux, et al., "HIV Infection with Seroconversion After a Superficial Needlestick Injury to the Finger," New England Journal of Medicine 315:9 (August 28, 1986), 582.

[15] Centers for Disease Control, "Apparent Transmission of Human T-Lymphotropic Virus Type III/Lymphadenopathy-Associated Virus from a Child to a Mother Providing Health Care," Morbidity and Mortality Weekly Report 35:5 (February 7, 1986), 76-79.

[16] P. Grint and M. McEvoy, "Two Associated Cases of the Acquired Immune Deficiency Syndrome (AIDS)," Communicable Disease Report 42 (1985), 4.

[17] Centers for Disease Control, "Update: Human Immunodeficiency Virus Infection in Health-Care Workers Exposed to Blood of Infected Patients."

[18] V.M. Napoli and John E. McGowan, "How Much Blood Is in a Needlestick?" Journal of Infectious Diseases 155:4 (April 1987), 828.

[19] Centers for Disease Control, "Recommendations for Prevention of HIV Transmission in Health-Care Settings."

[20] George F. Grady, V.A. Lee, A.M. Prince, et al., "Hepatitis B Immune Globulin for Accidental Exposures among Medical Personnel--Final Report of a Multicenter Controlled Trial," Journal of Infectious Diseases 138:5 (November 1978), 625-38; L.B. Seeff, E.C. Wright, H.J. Zimmerman, et al., "Type B Hepatitis After Needlestick Exposure--Prevention with Hepatitis B Immune Globulin," Annals of Internal Medicine 88:3 (March 1978), 285-93; B.G. Werner and George F. Grady, "Accidental Hepatitis-B-Surface-Antigen-Positive Inoculations: Use of e Antigen to Estimate Infectivity," Annals of Internal Medicine 97:3 (September 1982), 367-69.

[21] Weiss, Saxinger, Rechtman, et al., "HTLV-III Infection among Health-Care Workers."

[22] Centers for Fisease Control," Recommendations for Prevention of HIV Transmission in Health-Care Settings."

James R. Allen is a physician with the AIDS Program at the Centers for Disease Control, Atlanta, GA.
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Title Annotation:human immunodeficiency virus
Author:Allen, James R.
Publication:The Hastings Center Report
Date:Apr 1, 1988
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