CDC NATIONAL AIDS HOTLINE TRAINING BULLETIN #5 - May 15, 1992
Centers for Disease Control and Prevention

1. How many HIV-infected health-care workers (HCWs) have infected their patients in a health-care setting?

Transmission of HIV from a HCW to patients have been demonstrated in only one instance--the dental practice in Florida. The Centers for Disease Control (CDC) investigation concluded that HIV was transmitted from the dentist to patients, rather than from patient to patient; however, the specific events resulting in infection transmission are not known.

2. Did the 65 patients mentioned in the Annals of Internal Medicine editorial (or those in the Morbidity and Mortality Weekly Report [MMWR]), for whom no nonoccupational risk factor was identified, become infected from their HCW?

With the exception of the Florida case, thus far, none of the infected patients in the lookback investigations has been determined to have acquired HIV infection from a HCW.

3. Why are the numbers in the Annals editorial different from those in the MMWR?

These investigations are ongoing and the data are updated continuously. The numbers for the Annals are through March 1992 and the MMWR is updated to May 8, 1992.

4. Does this report mean that my risk of getting HIV infection from my HCW is 65/13,000 (or 23/15,795 in the MMWR)?

No, because none of the 65 patients has been demonstrated to have acquired infection from a HCW. The average risk of HIV transmission from an infected HCW to a patient during an invasive procedure is very small, estimated by CDC as about 1 in 42,000 to 1 in 420,000 procedures. The risk is likely to depend on a number of factors, including the type of procedure and the technique, skill, and medical condition of the HCW.

5. You say that the risk is small, but the risk in the Florida investigation was high, wasn't it?

The only recognized instance of HIV transmission from HCW-to- patient has occurred as a cluster of cases linked to one HCW. In this cluster, HIV was transmitted to 5 of 1,100 patients evaluated. A cluster is a group of cases linked to a particular HCW during a particular period of time. The risk of transmission is higher when receiving care from a HCW linked to a cluster. Reasons for increased infection transmission during clusters are not always known, but may include variations in technique, procedures performed, the infectivity of the HCW (i.e., amount of virus in his/her blood) and the susceptibility of the patient to infection. The risk of sporadic transmission (i.e., not associated with a cluster) has been estimated by CDC as about 1 in 42,000 to 1 in 420,000 procedures.

6. What were the occupations of the 27 HCW's mentioned in the Annals editorial? Did they all perform invasive procedures?

This information has been updated in the MMWR which states that the occupations of the 32 HCWs were: 16 dentists/dental student; 10 surgeons/obstetricians; and 6 physicians in nonsurgical specialties. The number of patients who underwent invasive procedures is not known.

7. In what cities/states/areas were these HCWs located?

These HCWs were located in many cities and states throughout the United States.

8. Does CDC plan to do genetic sequencing on the 65/75 patients?

DNA genetic sequencing is being conducted at CDC of some of the seropositive patients. Sequencing is conducted if indicated after epidemiologic investigations have been completed, and if appropriate specimens are available from both the HIV-infected HCW and the seropositive patient.

9. How many more cases of HIV infection in HCWs is CDC aware of?

The report in the MMWR summarizes data which were collected from investigations of patients tested for HIV who were treated by 32 HIV-infected HCWs. These are the investigations, to date, that CDC is aware of that have resulted in patient testing and for which results have been collected.

As of March 31, 1992, 8,088 HCWs with AIDS have been reported to CDC including 227 dental workers, 841 physicians and 56 surgeons. Of these, 163 dental workers, 577 physicians, and 42 surgeons are reported to have died.

10. Does CDC expect there to be other cases of HIV transmission from HCW to patient?

The risk of HIV transmission from HCW to patient is very small. While other cases may occur, this very small risk is minimized by careful adherence to CDC recommendations.

11. What does CDC recommend dentists/doctors do to protect their patients from infection?

CDC recommends that all HCWs use proper infection control technique, including the use of "Universal Precautions" for all patients. Specific recommendations for HIV-infected HCWs who perform invasive procedures were published in July, 1991; in response to comments received, revision of these recommendations is currently under discussion. Any revision of these guidelines will be released for public comment. No timetable has been specified.

12. If the risk is so small, why is this issue receiving so much attention?

Since virtually everybody receives medical and/or dental care at some point in their lives, the possibility of HIV transmission while receiving health care has led to concern.

TRANSMISSION IN DENTAL SETTINGS

13. What is the CDC's current position on the possibility of patient-to-patient transmission of AIDS via dental equipment?

Investigators at CDC are not aware of any studies that confirm the transmission of a blood-borne pathogen, such as hepatitis B virus (HBV) or HIV, through contaminated dental equipment. While reusable dental equipment that becomes contaminated with blood or tissue and is not appropriately cleaned and disinfected or sterilized between patients may have the potential to transmit infection to a subsequent patient, no such cases of patient-to-patient transmission have been reported in dental practice. Although the precise event(s) resulting in transmission of HIV to five patients of a Florida dentist with AIDS is unknown, results from the investigation do not suggest that HIV was transmitted from one patient to another patient by contaminated dental equipment.

14. Is work currently being done to formulate revised guidelines regarding heat sterilization or autoclaving of dental equipment. Will they be announced as early as May 30, 1992?

CDC is updating current recommendations for infection control in dentistry. CDC has always recommended thorough sterilization procedures. Although the basic principles of infection control remain unchanged, advances in dental materials and equipment require continual evaluation and updating of current practices. For example, CDC recommendations state that all heat-tolerant instruments should be cleaned and then treated between patients by a heating process capable of sterilization (e.g., steam autoclave). CDC has recommended since 1989 that dental handpieces which cannot be autoclaved only be used until they can be replaced by a handpiece that can be autoclaved. Components of all dental handpieces currently made in the U.S. are either heat-stable or can be replaced with components that are heat-stable. Earlier recommendations allowed for surface disinfection of handpieces that could not be autoclaved.

15. Has the CDC given consideration to guidelines involving check valves to prevent blood and saliva from being sucked back into dental equipment?

In the MMWR, April 18, 1986, Vol. 35, No. 15, pp. 237-242, CDC published the following recommendation for "check valves" in dental units:

Because water retraction valves within the dental units may aspirate infective materials back into the handpiece and water line, check valves should be installed to reduce the risk of transfer of infective material. While the magnitude of this risk is not known, it is prudent for water-cooled hand pieces to be run and to discharge water into a sink or container for 20-30 seconds after completing care on each patient. This is intended to physically flush out patient material that may have been aspirated into the handpiece or water line...

16. We have been informed that the CDC is currently conducting investigations in conjunction with state health agencies into cases involving possible HIV infection in dental practices. Is this correct?

In addition to the Florida dental investigation previously reported by the CDC, as of May 8, 1992, CDC has been notified of patient testing of 32 HIV-infected health-care workers (HCWs), which includes dentists and physicians. Investigations still in progress have not confirmed additional HIV transmission from a HCW to a patient.

17. In these investigations or any others, has the CDC so far found any evidence of patient-to-patient transmission of HIV via dental equipment?

The investigation of the dental practice in Florida is the only instance to date in which patients were infected with HIV during dental care. Results from this investigation support transmission of HIV from the dentist to the patients rather than from one patient to another patient by contaminated dental equipment.

18. We have been informed that the CDC has been planning to state in the MMWR that a patient of the Florida dentist was possibly contaminated by another patient. Is this true?

CDC has no evidence to suggest that HIV was transmitted from one patient to another patient by contaminated dental equipment and is not planning any such announcement in the MMWR.

19. Does the CDC feel that epidemiological evidence of patient-to-patient infection is necessary before any revision of sterilization guidelines? Why has it taken so long to come out with revised guidelines?

CDC periodically issues new, revised or updated guidelines and recommendations for infection control and disinfection and sterilization practices. CDC reviews its guidelines and recommendations as findings from epidemiologic investigations become available, but such findings are not necessary before such review. Recommendations for infection control practices for dentistry were published in 1986 and updated in 1987 and 1988, and in 1989 an infection control handbook that outlined practical decontamination procedures in the dental office was sent to dentists throughout the country. We continue to update guidelines resulting from technological advances in dental materials and equipment.

20. What significance does the CDC attribute to the forthcoming publication of a paper by Dr. David Lewis of the University of Georgia reporting that he has found the HIV virus surviving in dental equipment?

Dr. Lewis' study, currently submitted for publication, reconfirms past observations that dental handpieces and other instruments, such as prophylaxis angles, potentially may be contaminated with patient material during use. His study involved using dental instruments on patients infected with HIV, cleaning and disinfecting the external surfaces of the instruments, and then employing a very sensitive laboratory technique (i.e., polymerase chain reaction) to detect residual HIV genetic material from the internal surfaces; however, the laboratory technique used in this aspect of the study does not distinguish between live and dead HIV particles. Attempts to culture viable HIV from blood-contaminated prophylaxis angles were not successful. This study supports CDC recommendations (1986) for appropriate disinfection and sterilization of dental instruments.

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