HIV AND THE HEALTH CARE

 WORKER:

Transmission of HIV in the Health Care

http://aidscentral.com/

Steven C. Johnson, MD

University of Colorado Health Sciences Center, Infectious Disease Clinic

(Reprinted with permission from AIDS NEWSLINK, Mountain-Plains Regional AIDS Education and Training Center Newsletter, Spring 1996)

By December 31, 1995, the cumulative number of AIDS cases reported in the U.S. had exceeded 500,000. The CDC currently estimates that 1 million Americans are HIV-infected. Nearly all health care workers (HCWs) will be involved in some way with the care of these persons who require frequent visits to clinics and hospitals. This fact is illustrated by the "Sentinel Hospitals" study which measured HIV prevalence among hospitalized patients who were not known to be HIV-infected. The seroprevalence at these 26 hospitals varied from 0.1 percent to 7.85 percent and was as high as 21.7 percent in men aged 25 to 44 at one hospital¹. Well-documented cases of occupationally acquired HIV infection have understandably raised concerns among HCWs regarding their own safety. This article reviews the current data on occupational transmission of HIV infection, the current methods in place to protect HCWs, and the management of an occupational exposure to HIV when it occurs.

HIV Transmission from Patient to Health Care Worker

HIV has been isolated from a number of body fluids including blood, semen, vaginal secretions, saliva, breast milk, tears, urine, serum, cerebrospinal fluid, alveolar fluid and organs for transplantation. Transmission of HIV occurs predominantly through exposure to genital secretions (male to female, female to male, male to male), inoculation of blood or bloody body fluid (blood transfusion, intravenous drug use), or perinatal exposure (intrauterine, peripartum, breast feeding)². There is no evidence that health care workers are at risk of acquiring HIV infection from the routine contact that occurs through interview and physical examination of the patient. In addition, transmission from urine. tears. sweat. sputum, feces, or aerosolized patient secretions has never been documented. However, HCWs are at a small risk from parenteral or non-parenteral (cutaneous and mucous membrane) exposure to HIV-infected blood or bloody body fluids. Data regarding this risk are derived mainly from individual reports of HIV infection after occupational exposure and from several prospective studies of HCWs managing HIV-infected patients.

Seroconversion refers to the development of antibodies to HIV temporally related to an HIV exposure. There have been at least 49 occupational exposures to HIV in HCWs that have resulted in sero conversion³. Forty-two of the 49 cases were due to parenteral exposures (mainly needlestick), five were due to non-parenteral exposures, one-case had both exposures, and one case had an unknown method of exposure. Of the non-parenteral exposures, non-intact skin, a prolonged or intense blood exposure, or a lack of barrier protection can be cited as potential reasons for transmission⁴. Most of the exposures have been to HIV-infected blood or visibly bloody body fluid, although three HCWs were exposed to concentrated HIV preparations in scientific laboratories. In addition to these cases, there are other reports of occupational HIV infection that are less well-documented. Table 1 lists the occupations of those HCWs with documented and possible occupational HIV infection⁴.

Although these reports raise concerns, they provide little information on the magnitude of risk, given a denominator of 5 million HCWs in the U.S. Prospective studies of HCWs who have sustained an exposure to HIV-infected blood or bloody body fluid are the most important studies to define the risk of occupational transmission. Henderson and his colleagues have reviewed these studies, which are summarized in Table 2⁵.

It is notable that prospective studies have not documented a single case of HIV transmission after cutaneous or mucous membrane exposure to HIV-infected blood or body fluid. These studies illustrate the low risk of non-parenteral exposure. However, there have been six cases of percutaneous transmission documented, for a rate of 0.29 percent (approximately 1 in 300). A more recent report from the CDC (which includes some patients reported in reference 5) documents four seroconversions out of 1103 percutaneous exposures or a rate of 0.36 percent (upper limit of 95 percent CI, 0.83 percent)⁶.

Based on current data, the rate of HIV transmission after a single percutaneous exposure to HIV-infected blood is currently estimated at 1 in 300. However, each exposure is most likely a unique event with regard to the probability of HIV transmission. Factors that are thought to play a role in whether seroconversion occurs include the state of the HIV-infected patient (higher viral load during the acute seroconverting illness or in late stage HIV disease may increase the risk), the nature of the injury (most seroconversions have occurred with deep, IM needlesticks, especially if measurable quantities of blood have been inoculated), and recipient factors such as good wound care and the use of post-exposure chemoprophylaxis with AZT. In the absence of a deep injury or blood inoculation, the rate of HIV transmission for a "simple needlestick' may be less than 1 in 1,000⁷.

Minimizing the Risk of HIV Transmission to Health Care Workers

For any occupation, it is never possible to guarantee a risk-free environment. In the course of patient care, HCWs may be exposed to a diverse group of occupational hazards that include patient violence, ionizing radiation, anti-neoplastic drugs, anesthetic gases, and infectious agents such as HIV, hepatitis B virus (HBV), and Mycobacterium tuberculosis⁸. As illustrated in Table 3, when compared to HIV, hepatitis B virus is a particularly serious occupational hazard^9,10.

In addition, needlestick transmission of hepatitis C to HCWs has been recently reported^11,12. Because of the potential risk posed by a number of pathogens besides HIV, the CDC in 1987 recommended the use of "Universal Blood and Body Fluid Precautions"^13,14. The premise of universal precautions (UP) is that all blood or body fluids may potentially contain a transmissible agent and HCWs should institute protective measures to limit all exposures. Guidelines include:

1. Gloves should be worn when contact with blood or body fluids is anticipated. For procedures where splashing might occur, additional barrier techniques such as masks, gowns, or eyewear should be used.
2. Hands or other skin surfaces should be washed immediately if contaminated by blood or other body fluid. Hands should be washed immediately after gloves are removed.
3. All HCWs should take precautions to avoid injuries from needles, scalpels, or other sharp devices. Needles should not be recapped or otherwise manipulated. Puncture-resistant containers should be available for sharp instruments.
4. Ventilation devices should be available for resuscitation.
5. HCWs who have exudative lesions or weeping dermatitis should refrain from all direct patient care.
6. Pregnant HCWs are not known to be at greater risk of acquiring HIV infection, but strict adherence to universal precautions is recommended.

Despite the widespread implementation of UP, there is considerable controversy about their effectiveness. UP appear to decrease the rate of cutaneous and mucous membrane exposures, but needlestick injuries have remained frequent^15,16 . In reviewing the circumstances surrounding injuries, emergency situations such as cardiopulmonary resuscitation seem to be particularly high risk. Careless practices such as blindly passing sharp instruments or leaving instruments in bedding or partially hidden among supplies also are frequently implicated. In preparing for prouedures that use sharp instruments, it is important to plan ahead so that puncture-resistant sharps containers are available and that sharps are disposed of immediately after use.

A promising approach to decreasing the number of needlestick injuries involves new technologies. One such system is a "needleless" IV system which uses clamps, screw devices and shielded needles to decrease the possibility of needIestick injury. Other areas of development are gloves that are impregnable to needles or contain a virucidal compound. Advances in these areas have the potential to produce a safer workplace. However, they are likely to be expensive.

Management of Needlestick and Other Significant Exposures

Despite attempts to minimize the risk, occupational needlesticks and other sharp injuries continue to occur. In the event of a needlestick or other significant exposure to blood or body fluid, an assessment must be immediately performed to determine the risk of transmission of HIV and other blood-borne pathogens, and to determine the need for therapy¹⁷.

The first step is to review the circumstances of the injury to ensure that it is a significant exposure. HCWs may seek evaluation for exposures that may not be significant. Significant exposures generally involve parenteral or non-parenteral contact to blood or body fluid. All parenteral exposures are considered significant. For non-parenteral exposure, contact with the eyes, mouth, other mucous membranes, or broken areas of skin are considered sianificant. If the exposure is judged not to be significant, reassurance may be all that is necessary.

For significant exposures, the next step is to conduct a clinical and epidemiological assessment of the source patient. This includes a review of known or suspected diseases, assessment of risk factors for the common blood-borne infections (HIV, HBV and HCV), and a review of previous serological testing. Complete data regarding the source of the exposure will not be present in all cases and serologic tesing of the source patient may be necessary. State laws vary regarding the need for informed consent in this setting. Clinical judgement on empiric treatment may be necessary in situations where data regarding the source patient are unknown or incomplete.

The next step is to review the medical history of the HCW and make decisions regarding treatment. As hepatitis B is the only one of the three common blood-borne pathogens where treatmnt of exposures is known to be effective, it is extremely important to identify HCWs who are non-immune to HBV and may benefit from post exposure prophylaxis with hepatitis B immune globulin (HBIG). It should be given as soon as possible, preferably within one week of exposure. However, its efficacy is not known, there are know failures, and it is currently not recommended¹⁷.

In individuals who sustain a significant exposure to HIV-infected blood or body fluid, post-exposure chemoprophylaxis with AZT (zidovidine) and/or other antiretroviral therapy should be strongly considered¹⁸. This has been recommended for more than five years, although it has been controversial because of lack of known efficacy. Until recently, the only evidence of benefit came from experimental animal studies. In addition, known seroconversions despite AZT therapy have been well described⁶. However, a recently reported case-control study found the use of AZT reduced the risk of HIV transmission by 79 percent (95 percent, CI=43-94 percent)¹⁹. Although there are potential limitations to this study, it is the first analysis to suggest a treatment benefit.

Given the recent developments of new, more potent antiretroviral agents and the established benefit of combination therapy in other settings, the optimal treatment regimen for post-exposure chemoprophylaxis is unclear. Zidovudine as a single agent is a relatively weak inhibitor of HIV and the source may transmit an AZT-resistant virus. This is especially a concern if the source patient has been on prolonged AZT treatment. Combinations of agents should be a more effective strategy. Some hospitals are already using a combination of AZT and 3TC (lamivudine) for post-exposure prophylaxis. However, inhibition of HIV is even better with regimens that include one of the new protease inhibitors (ritonavir or indinavir). A combination of AZT, 3TC, and either ritonavir or indinavir seems to be the optimal regimen at the present time, although side effects may limit this approach in some individuals. Most regimens are given for at least four weeks. For exposures more than 72 hours old, post-exposure prophylaxis is generally not recommended.

Regardless of treatment, HIV serologic testing, should be done at baseline and then at three and six months. The likelihood of seroconversion after six months is extremely rare, and extending the period of observation to 12 months doubles the time that the HCW must be anxious about this situation. Although the likelihood of HIV transmission will be rare, HCWs should be counseled regarding safer sex in order to prevent further transmission. Not surprisingly, this is an extremely frightening situation for most individuals and emotional and psychological support are an important part of the management.

Summary

HIV can be transmitted from patients to HCWs through parenteral and nonparenteral exposure to blood or body fluid. The only measurable risk is through percutaneous exposure to HIV-infected blood with a rate of transmission of approximately 1 in 300 episodes. Hepatitis B is currently a greater occupational risk.

Avoidance of injury with contaminated sharp devices is the single most important measure in preventing transmission of HIV, hepatitis B, and hepatitis C in the workplace. The practice of universal precautions is an important measure in preventing non-parenteral exposures. Hepatitis B vaccination should be universal.

In the event of a significant exposure, a detailed risk assessment is necessary to reach decisions on treatment. In the event of exposure to HIV, components of management should include a risk assessment of the event to determine likelihood of transmission, a discussion of post-exposure chernoprophylaxis with antiretroviral agents, emotional and psychological counseling and support, counseling on safer sex practices during the period of monitoring, and close medical followup with repeat serologic testing.

When kept in its proper perspective, the occupational risk of HIV infection is very low. An awareness of this risk and the measures in place to keep it acceptably low should allow all HCW`s to continue to provide compassionate care for individuals with HIV infection without undue concern for their own personal safety.

References

1 . St. Louis ME, et al. Seroprevalence Rates of Human Immunodeficiency Virus Infection at Sentinel Hospitals in the United States. N Engl J Med 1990;323:213.

2. Friedland GH, Klein RS. Transmission of the Human Immunodeficiency Virus. New Engl J Med 1987;317:1125.

3. CDC. HIVIAIDS Surveillance Report, 1995;7(no.2):2 1.

4. CDC. Update: HIV Infections in Health Care Workers Exposed to Blood of Infected Patients. MMWR 1987;36:285.

5. Henderson bK, et al..Risk for Occupational Transmission of Human Immunodeficiency Virus Type I (HIV-1) Associated with Clinical Exposures. Ann Intern Med 1990; 1 13:740.

6. Tokars JI', et al. Surveillance of HIV Infection and Zidovudine Use Among Health Care Workers After Occupational Exposure to HIV-infected Blood. Ann Intern Med 1993-,118:913.

7. WhiteAC. HIV Infection After Needlesticks. Ann lntem Med l991;114:253.

BellDM. HIV Transmission in Health Care Settings:Risk and Risk Reduction. Am J Med 199 1;9 1 (suppl 3B):294S.