CDC received a case report of acquired immunodeficiency syndrome (AIDS) in a young woman for whom an epidemiologic investigation had not established a source for her human immunodeficiency virus (HIV) infection (i.e., documented behavioral or other risk factors, including intravenous (IV)-drug use, sex with an HIV-infected person, or receipt of a blood transfusion or blood components). However, investigation revealed that 24 months before her AIDS diagnosis she had two teeth extracted by a dentist who had AIDS. Information on the dental procedure was obtained from interviews with the patient and reviews of her dental records and radiographs. This report summarizes the epidemiologic and laboratory findings of the investigation.*

The patient had two maxillary third molars extracted under local anesthesia in the dentist's office. The dentist had been diagnosed with AIDS 3 months before performing the procedure. Written documentation of the procedure was limited. Review of the radiographs indicated that the maxillary third molars were not impacted in bone. The patient reported that she received no general anesthetic or sedative and that during the procedure the dentist wore gloves and a mask. She did not recall, nor did review of the dental records reveal, any circumstances 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). The patient had not received dental care from this dentist before the dental extractions.

Four weeks after the dental procedure, the patient sought medical evaluation for a sore throat. Review of her medical records revealed that she was afebrile, with moderately enlarged tonsils with ulcerations and moderately enlarged nontender anterior cervical lymph nodes. Rash, generalized lymphadenopathy, or fatigue were not reported or noted on the medical record. A "strep antigen" test was negative. The patient was diagnosed with pharyngitis and aphthous ulcers. Seventeen months after the procedure, she was diagnosed with oral candidiasis; 24 months after the procedure, she was diagnosed with Pneumocystis carinii pneumonia and was seropositive for HIV antibody. The patient reported no previous test for HIV infection.

Multiple interviews of the patient and her family and friends by health department staff and review of her medical and previous dental records did not identify factors that may have potentially placed her at risk for HIV infection. The patient reported no history of blood transfusions, IV-drug use, acupuncture, tattoos, or artificial insemination. Additionally, she denied a history of sexually transmitted diseases or pregnancies. VDRL and hepatitis B serologies were negative. The patient has never been employed in a health-care or other setting where she could have been exposed to HIV-infected blood or other body fluids. She reported two boyfriends before her diagnosis of AIDS; both were tested for HIV infection and were seronegative.

Blood specimens were obtained from the patient and the dentist. To determine the relatedness of the HIV strains from both persons, DNA was extracted from their peripheral blood mononuclear cells (PBMC). HIV sequences encoding the variable regions (V3, V4, and V5) and a constant region (C3) of the major external glycoprotein gp120 were selectively amplified using the polymerase chain reaction (PCR) (1). Amplified HIV DNA was molecularly cloned, and nucleotide sequences of multiple clones were determined. The relatedness of the sequences was analyzed by several computer-based methods in collaboration with Los Alamos National Laboratory.** This multifaceted analysis showed a similarity between the sequences from the patient and the dentist that was comparable to what has been observed for cases that have been epidemiologically linked (Los Alamos National Laboratory, unpublished data). Although the viral sequences from the dentist and the patient could be distinguished from each other, they were closer than what has been observed for pair-wise comparisons of sequences taken from the other North American isolates studied (3). Reported by: 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: The case reported here is consistent with transmission of HIV to a patient during an invasive dental procedure, although the possibility of another source of infection cannot be entirely excluded. No case of such transmission has been previously described.

In this report, the possibility that the patient may have been infected with HIV during the dental procedure is based on the following considerations: 1) the patient had an invasive procedure performed by a dentist with AIDS (such procedures have been associated with transmission of hepatitis B virus, which is also a bloodborne pathogen, to patients); 2) an epidemiologic investigation did not identify any other risk factors or behaviors that may have placed the woman at risk for HIV infection; and 3) viral DNA sequences from the patient and the dentist were closely related. These three considerations are discussed as follows.

First, although the dentist was infected with HIV, it is uncertain whether the patient was exposed to the dentist's blood during the extraction procedure. When interviewed more than 2 years after the procedure, the patient recalled that the dentist wore gloves and a mask. The dental records contained few details on the extraction procedure, but there was no mention of any circumstances that may have exposed the patient to the dentist's blood. Review of the dental records and radiographs suggest that the extraction should have been uncomplicated.

The dentist recalled occasional needlesticks with narrow-gauge needles used to administer local anesthetic. After the diagnosis of HIV infection, however, the dentist did not recall sustaining a needlestick or cut resulting in visible blood during a procedure. The dentist, who is negative for hepatitis B surface antigen, is no longer in practice. Although the dentist employed assistants, it could not be determined whether or to what extent the dentist was assisted in the procedure reported here; it is not known whether the assistants were tested for HIV infection. Details of the disinfection and sterilization practices of the dental office are unknown.

Second, although multiple interviews with this patient and other persons did not identify any established risk factors for HIV infection, such risk factors involve sensitive personal behaviors that may not always be revealed during interviews. In addition, the patient's HIV-infection status at the time of the dental procedure is unknown. The possibility that the patient may have been infected through another mode cannot be entirely excluded.

Third, the DNA sequence data indicate a high degree of similarity between the HIV strains infecting the patient and the dentist. HIV-1 exhibits considerable genetic variability, particularly in the selected regions of the envelope gene tested. This property may be helpful in evaluating the relatedness of viral strains isolated from different persons (2). However, use of DNA sequencing for this purpose is new, and there is a paucity of sequence data pertaining to the HIV-1 viruses of sex partners and other epidemiologically related patients. The quantitative criteria for determining epidemiologic linkage based on HIV sequences are just now being developed.

In addition, the occurrence of pharyngitis 4 weeks after the dental procedure is consistent with an acute retroviral syndrome following HIV infection. However, the symptoms in this patient did not include fever, rash, or generalized lymphadenopathy, which have been described in most cases of acute retroviral syndrome (4). Also, the time between the dental procedure and the development of AIDS (24 months) was short; 1% of infected homosexual/bisexual men and 5% of infected transfusion recipients develop AIDS within 2 years of infection (5,6).

Prospective investigations of HIV transmission from patients to health-care workers indicate that the risk for HIV transmission after percutaneous exposure to HIV-infected blood averages 0.4% (7). Four investigations have been reported that attempted to assess the risk of HIV transmission from infected health-care workers to their patients (8-11). In the largest study, 616 patients who underwent surgery by a general surgeon during the 7 years preceding his diagnosis of AIDS were tested for HIV antibody. One patient, an IV-drug user, was positive for HIV antibody (8). Viral strains from the patient and the surgeon were not characterized.

Transmission of hepatitis B virus (HBV), which has epidemiologic transmission patterns similar to HIV, from health-care workers to patients during invasive medical (primarily gynecologic surgery) and dental (primarily oral surgery) procedures has been reported (12-15). The dental procedures in which HBV was transmitted involved oral surgical procedures such as dental extractions. In these reported instances, the dental workers did not routinely wear gloves and were thought to have sustained puncture wounds or had skin lesions or microlacerations that allowed virus to contaminate instruments or open wounds of patients. Also, these health-care workers (when tested) have been positive for hepatitis B e antigen, a marker that indicates very high titers of virus in blood and correlates with increased transmissibility of HBV.

Restrictions on patient care for health-care workers with HIV infection have been considered by the American Medical Association (16), the American Hospital Association (17), the American Dental Association (18), the American College of Obstetricians and Gynecologists (19), the British government (20), CDC (21), and other organizations. Although the specific recommendations of these organizations vary to some extent, these recommendations generally have stated that the risk, if any, of HIV transmission from health-care workers to patients occurs during invasive procedures and that decisions regarding restrictions of patient care by infected workers who perform such procedures should be made on an individual basis.

The epidemiologic and laboratory findings in this investigation indicate possible transmission of HIV from the dentist to the patient. Regardless of the interpretation of the findings in this investigation, adherence to universal precautions, including prevention of blood contact between health-care workers and patients and proper sterilization and disinfection of patient-care equipment, is important for prevention of transmission of bloodborne pathogens in health-care settings (21-23). CDC is considering the implications of this case in its review of the guidelines for prevention of transmission of HIV and other bloodborne pathogens to patients during invasive procedures.

References

1. Ou CY, Kwok S, Mitchell SW, et al. DNA amplification for direct

detection of HIV-1 in DNA of peripheral blood mononuclear cells. Science 1988;239:295-7.

2. Burger H, Belman A, Grimson R, et al. Long HIV-1 incubation periods and dynamics of transmission within a family. Lancet 1990;336:134-6.

3. Myers G, Rabson AB, Josephs SE, Smith TF, Berzofsky JA, Wong-Staal F. Human retroviruses and AIDS, 1989. Los Alamos, New Mexico: Los Alamos National Laboratory, Theoretical Division, 1989.

4. Cooper DA, Gold J, MacLean P, et al. Acute AIDS retrovirus infection: definition of a clinical illness associated with seroconversion. Lancet 1985;1:537-40.

5. Lifson AR, Hessol N, Rutherford G, et al. Natural history of HIV infection in a cohort of homosexual and bisexual men: clinical and immunologic outcome, 1977-1990 (Abstract). Vol 1. VI International Conference on AIDS. San Francisco, June 20-24, 1990:142.

6. Ward JW, Bush TJ, Perkins HA, et al. The natural history of transfusion-associated infection with human immunodeficiency virus: factors influencing the rate of progression to disease. N Engl J Med 1989;321:947-52.

7. Marcus R, the CDC Cooperative Needlestick Surveillance Group. Surveillance of health care workers exposed to blood from patients infected with the human immunodeficiency virus. N Engl J Med 1988;319:1118-23.

8. Mishu B, Schaffner W, Horan J, Wood L, Hutcheson R, McNabb P. A surgeon with AIDS: lack of transmission to patients. JAMA 1990;264:467-70.

9. Sacks JJ. AIDS in a surgeon (Letter). N Engl J Med 1985;313:1017-8. 10. Armstrong FP, Miner JC, Wolfe WH. Investigation of a health-care worker with symptomatic human immunodeficiency virus infection: an epidemiologic approach. Military Med 1988;152:414-8. 11. Porter JD, Cruickshank JG, Gentle PH, Robinson RG, Gill ON. Management of patients treated by a surgeon with HIV infection (Letter). Lancet 1990;335:113-4. 12. Welch J, Webster M, Tilzey AJ, Noah ND, Banatvala JE. Hepatitis B infections after gynaecological surgery. Lancet 1989;1:205-7. 13. Shaw FE Jr, Barrett CL, Hamm R, et al. Lethal outbreak of hepatitis B in a dental practice. JAMA 1986;255:3260-4. 14. Kane MA, Lettau LA. Transmission of HBV from dental personnel to patients. J Am Dent Assoc 1985;110:634-6. 15. Ahtone J, Goodman RA. Hepatitis B and dental personnel: transmission to patients and prevention issues. J Am Dent Assoc 1983;106:219-22. 16. American Medical Association. Ethical issues in the growing AIDS crisis: Council on Ethical and Judicial Affairs. JAMA 1988;259:1360-1. 17. American Hospital Association. Management of HIV infection in the hospital. 3rd ed. Chicago: American Hospital Association, 1988. 18. American Dental Association. Report of the Council on Ethics, Bylaws, and Judicial Affairs: American Dental Association annual reports and resolutions. Chicago: American Dental Association, 1990:147-9. 19. Committee on Ethics, The American College of Obstetricians and Gynecologists. Human immunodeficiency virus infection: physicians' responsibilities. Obstet Gynecol 1990;75:1043-5. 20. Department of Health and Social Security. AIDS: HIV-infected health care workers--report of the recommendations of the Expert Advisory Group on AIDS. London: Her Majesty's Stationery Office, 1988. 21. CDC. Recommendations for prevention of HIV transmission in health-care settings. MMWR 1987;36(no. 2S). 22. CDC. Update: universal precautions for prevention of transmission of human immuno deficiency virus, hepatitis B virus, and other bloodborne pathogens in health-care settings. MMWR 1988;37:377-82,387-8. 23. CDC. Guidelines for prevention of transmission of human immunodeficiency virus and hepatitis B virus to health-care and public safety workers. MMWR 1989;38(no. S-6).

• Single copies of this article will be available free until July 27, 1991, from the National AIDS Information Clearinghouse, P.O. Box 6003, Rockville, MD 20850; telephone (800) 458-5231. **Viral sequences obtained from the samples taken from the dentist and the patient were shown to be distinct by the following criteria:

1. Each PBMC sample was split into two before extraction of DNA. PCR amplification of human leukocyte antigen (DQ alpha) sequences was performed on each sample. The sequences were the same between samples from the same person, but the dentist and patient DNA samples were clearly different.

2. The average difference (4.6%, range: 2.0%-7.2%) between all viral V4-C3-V5 sequences present in the patient versus all those in the dentist was higher than the average difference between the viral sequences present within the dentist alone (3.5%, range: 1.2%-6.0%) and within the patient alone (2.0%, range: 0.4%-3.6%).

3. Viral sequences in the patient possessed some unique substitutions not found in the viral sequences from the dentist, and vice versa.

Viral sequences obtained from the samples taken from the dentist and the patient were judged to be closely related by the following criteria:

1. Individual consensus sequences deduced from single base

substitutions (excluding insertions and deletions) in the patient's and dentist's viral sequence sets over the V3-V4-C3-V5 regions of the envelope gene differed by 1.2%. Corresponding DNA regions from 17 other distinct North American isolates gave pair-wise differences to the dentist's consensus viral sequence of 5.1%-10.2%, with an average of 8.1%. Similarly, comparison of the patient's consensus viral sequence to these 17 gave pair-wise differences of 5.9%-10.7%, with an average of 8.8%. The range of all pair-wise differences among the 17 was 4.7%-12.9%, with an average of 9.2%. 2. Unique patterns of nucleotide substitutions not found in any other virus isolate examined were shared between viral sequences found in the dentist and patient. 3. The average difference (4.6%) between all of the patient's viral sequences and all of the dentist's viral sequences over the V4-C3-V5 regions falls into a class of differences (3.4%-5.8%) similarly determined for viruses from known epidemiologically linked cases (2; Los Alamos National Laboratory, unpublished data). These include two instances of sexual transmission, one instance of perinatal transmission, and an instance in which a group of persons with hemophilia became infected from a single batch of factor VIII concentrate.

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