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Epidemiologic Notes and Reports Update: Transmission of HIV Infection During Invasive Dental Procedures --- Florida

MMWR 40(23);377-381

Publication date: 06/14/1991

Table of Contents


Editorial Note




Previous reports from an epidemiologic investigation in Florida strongly suggested that three patients (patients A, B, and C) became infected with human immunodeficiency virus (HIV) while receiving dental care from a dentist with acquired immunodeficiency syndrome (AIDS) (1,2). This report describes findings that suggest HIV was transmitted to two additional patients (patients E and G). These two patients had no other confirmed exposures to HIV, had invasive procedures performed by the dentist, and are infected with HIV strains that are closely related genetically to the strains from the three previously reported patients and from the dentist (Table 1). In addition, this report describes the epidemiologic and laboratory investigation of another HIV-infected patient of the dentist (patient F).

Patient E

Patient E, a young woman, contacted CDC after the initial report of a possible transmission of HIV in this dental practice (1,2). She denied a history of transfusion, receipt of blood products, or injecting drug use. She did not report a history of an illness compatible with an acute retroviral syndrome. She was seropositive for antibody to HIV when first tested in October 1988; in January 1991, she was asymptomatic, with greater than 500 CD4 lymphocytes per mm3; serologic tests for syphilis and hepatitis B virus infection were negative.

Patient E's known former sex partners since 1981 were tested for HIV antibody (except one, who died from non-HIV--related causes in 1982 and was not known to be at high risk for HIV infection); one was positive. This man (patient F) was also a patient of the dentist. Patient E reported infrequent sexual contact with patient F; the last contact was in the fall of 1988.

Patient F

Patient F had tested negative for HIV antibody in October 1988 (when patient E tested seropositive) and December 1988 but tested positive in December 1990. Review of his medical records indicated that, in September 1989, he sought medical care for a 1-week history of sore throat, loose stools, and headache; other symptoms included decreased appetite, fatigue, myalgias, and an earache. On examination, he was febrile (100.5 F (38.1 C)) and had tender anterior cervical adenopathy; his white blood cell count was 3300/mm3 (normal: greater than 4000 cells/mm3) with a lymphocyte count of 693/mm3 (normal: greater than 1000/mm3). He was diagnosed as having tonsillitis; throat culture yielded ``normal respiratory flora.'' No HIV-antibody test was performed at the time, nor is there any indication that an acute retroviral syndrome was considered. This illness occurred approximately 1 year after patient F's last reported dental appointment and his last sexual contact with patient E and 9 months after his last negative test for HIV antibody.

On interview, patient F denied a history of having had sex with men and injecting drug use. He had no history of blood transfusions or receipt of blood products. Review of medical and other records, however, indicated behavioral risk factors for HIV infection unacknowledged at the time of interview. In January 1991, his CD4 lymphocyte count was 253 cells/mm3, and serologic tests for syphilis and hepatitis B were negative.

Patient G

Patient G is a young man who contacted CDC after he tested positive for HIV antibody. In November 1990, he was first determined to be HIV seropositive when screened for plasma donation. He denied a history of having had sex with men, injecting drug use since 1977, blood transfusions, or receipt of blood products. He did not report a history of an illness compatible with an acute retroviral syndrome. Records indicate that when he donated blood in 1986 he was seronegative for syphilis, hepatitis B, and HIV. He reported having two female sex partners since 1986; both were seronegative for HIV antibody when tested in March and April 1991. In May 1991, his CD4 lymphocyte count was 400 cells/mm3, and serologic tests for syphilis and hepatitis B were negative.

Additional Information from Patient Interviews

Patients E and F were interviewed under circumstances that included the presence of other persons. Despite these circumstances, patients E and F, as well as patient G, reported nonparenteral use of illicit drugs. None, however, reported needlesharing or injecting illicit drugs. All of the patients denied sexual contact with the dentist.

Dental History of Patients

Patient records from the dental practice for patients E, F, and G could not be located. However, patient billing information was available for some of the reported patient visits. Billing information indicated that patient E made at least 10 visits to the dentist for examination, prophylaxis, fluoride treatment, restorative fillings and crowns, and root canal therapy from June through December 1988. She received local anesthetic, stated that the dentist wore gloves and a mask, and did not recall any specific incidents that would have exposed her to the dentist's blood (i.e., an injury to the dentist, such as a needlestick or cut with a sharp instrument).

Patient F reported having made five or six visits to the dentist during July and August 1988 for examination and radiographs, prophylaxis, extraction, restorative fillings, and root canal therapy. However, only one visit could be documented by billing records.

Medical records and billing information indicate that patient G made two visits to the dentist in July 1988 for root canal therapy and one restorative filling under local anesthetic. He could not recall whether the dentist wore gloves and a mask during the visits or any specific incidents that would have exposed him to the dentist's blood.

Laboratory Investigation

This investigation previously included sequencing of HIV proviral DNA in the lymphocyte samples obtained from the dentist, patients A, B, and C, and seven Florida control patients (1,2). Proviral DNA obtained from the lymphocytes from patients E, F, and G and from 24 additional control patients in Florida was performed using previously described methods (2,3) or a modification of these methods.* The sequences of 240 nucleotides from the V3 region of the gene encoding the viral external envelope glycoprotein, gp120, were then analyzed at Los Alamos National Laboratory.

Based on this analysis, the viral nucleotide sequences from patients E and G were determined to be closely related to those of the dentist, with average differences of 2.5% and 4.6%, respectively. The sequences from patients E and G were distinct from all sequences of the 31 local controls, with average differences of 9.4% and 11.2%, respectively. In addition, the HIV V3 peptides of the dentist and patients A, B, C, E, and G shared a unique pattern of eight noncontiguous amino acids (signature pattern) that has not been found in any other HIV sequence published or included in the HIV sequence database at Los Alamos National Laboratory. Sequence analysis indicated that the virus from patient F was not closely related to that of the dentist (average difference of 9.2%) nor to those of patients A, B, C, E, or G and lacked the unique pattern of amino acids identified in the viruses of the other patients and the dentist.

Reported by: JJ Witte, MD, Florida Dept of Health and Rehabilitative Svcs. KR Wilcox Jr, MD, State Epidemiologist, Michigan Dept of Public Health. Div of HIV/AIDS and Hospital Infections Program, Center for Infectious Diseases; Dental Disease Prevention Activity, Center for Prevention Svcs; National Institute for Occupational Safety and Health, CDC.

Editorial Note

Editorial Note:

This investigation strongly suggests that five patients (patients A, B, C, E, and G) became infected with HIV while receiving care from a dentist with AIDS. None of the five patients had other confirmed exposures to HIV, all had invasive procedures performed by the dentist, and all were infected with HIV strains that were closely related to each other and to the strain infecting the dentist but distinct from viruses obtained from control patients living in the same geographic area as the dental practice. In addition, patient G was known to have been HIV seronegative before being treated by the dentist.

Based on the following considerations, patient F does not appear to have been infected in the dental practice or through sexual contact with patient E: 1) he is infected with a strain of HIV that is not closely related genetically to that of the dentist and the other patients, including patient E; 2) he had other behavioral risk factors for HIV infection; and 3) he had an illness compatible with an acute retroviral syndrome approximately 1 year after his last reported dental visit and his last reported sexual contact with patient E.

The dentist's practice opened in 1981; although his first reported positive HIV test was documented in late 1986, the date of onset of his HIV infection is unknown (2). Each of the five patients (patients A, B, C, E, and G) had invasive procedures performed after the dentist had been diagnosed with AIDS in September 1987; four of the five made visits exclusively during a 21-month period (from November 1987 through July 1989). Patients E and G appear to have been infected in the summer of 1988. Therefore, transmission occurred relatively late in the course of the dentist's infection.

This is the only investigation in which transmission of HIV from an infected health-care worker to patients during invasive procedures has been strongly suggested. Neither the precise mode of HIV transmission to these patients nor the reasons for transmission to multiple patients in a single practice are known. However, hepatitis B virus, a bloodborne pathogen that is transmitted by routes similar to those of HIV, also has been transmitted to multiple patients in the practices of individual infected health-care workers during invasive procedures (4--6). Factors that may be associated with transmission of bloodborne pathogens from infected health-care workers to patients may reflect variations in the procedures performed and techniques used by the health-care worker, infection-control precautions used, and the titer of the infecting agent.



  1. CDC. Possible transmission of human immunodeficiency virus to a patient during an invasive dental procedure. MMWR 1990;39:489--93.
  2. CDC. Update: transmission of HIV infection during an invasive dental procedure---Florida. MMWR 1991;40:21--7,33.
  3. Ou CY, Kwok S, Mitchell SW, et al. DNA amplification for direct detection of HIV-1 in DNA of peripheral mononuclear cells. Science 1988;239:295--7.
  4. Grob P, Bischof B, Naeff R. Cluster of hepatitis B transmitted by a physician. Lancet 1981; 2:1218--20.
  5. Rimland D, Parkin WE, Miller GB, et al. Hepatitis B outbreak traced to an oral surgeon. N Engl J Med 1977;296:953--8.
  6. Ahtone J, Goodman RA. Hepatitis B and dental personnel: transmission to patients and prevention issues. J Am Dent Assoc 1983;106:219--22.

*In the initial sequencing of the HIV proviral DNA from patients E, F, and G, proviral DNA that had been amplified by the polymerase chain reaction (PCR) was molecularly cloned before it was sequenced. Unique sequences were included in the PCR primers used for amplification to distinguish the amplified product of each patient\'s specimen. To verify these results, additional blood samples obtained from patients F and G and a second aliquot of the initial blood sample from patient E were reanalyzed. In this reanalysis, amplified HIV DNA was sequenced directly, without molecular cloning. In each case, consensus sequences from the reanalysis were virtually identical to the initial sequence results. Sequencing of amplified proviral DNA from 24 control patients was also done directly. None of the proviral sequences from the dentist, patients A--G, and the 31 local controls were identical, indicating that the specimens had not been cross-contaminated. In addition, the proviral sequences from the dentist and the seven patients were reproduced in repeat analyses, providing further evidence of absence of crosscontamination.


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