Mycobacterium tuberculosis, the organism

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1 ARTICLE 4 An epidemiologic investigation of occupational transmission of Mycobacterium tuberculosis infection to dental health care personnel Infection prevention and control implications Jennifer L. Merte, MPH; Catherine M. Kroll, MPH; Amy S. Collins, MPH; Alan L. Melnick, MD, MPH Mycobacterium tuberculosis, the organism responsible for tuberculosis (TB), can spread through the air when a person with active pulmonary or laryngeal TB disease coughs, sneezes or sings. 1 Local public health departments have legally mandated responsibilities to prevent and control communicable diseases, including TB, in their communities. To fulfill this role, public health departments conduct TB contact investigations to identify people who have been exposed and people who are infected and might benefit from treatment of latent TB infection (LTBI). TB contact investigations are an essential component of the U.S. strategy for TB control and elimination. Groups whose risk of developing TB infection is higher than that of the general population include people born outside the United States (hereafter called foreign-born ), residents and employees of high-risk congregate settings (such as correctional facilities, long-term care facilities and homeless shelters), health care workers serving patients at high risk of developing TB, and health care workers who have had an unprotected exposure to M. tuberculosis. 1 In 2010, 396 (4.1 percent) of 9,666 U.S. adults older than 15 years who reported having active TB and for whom occupational data were available were health care workers. 2 In 1994, the Centers for Disease Control and Prevention (CDC) published Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Healthcare Facilities, In 2005, CDC revised the guidelines to reflect the shifts in the epidemiology of TB, advances in scientific understanding and changes in health care practices in the United States. The new guidelines addressed all settings in which ABSTRACT Background. The authors describe an investigation of a dental hygienist who developed active pulmonary tuberculosis (TB), worked for several months while infectious and likely transmitted Mycobacterium tuberculosis in a dental setting in Washington state. Methods. Clark County Public Health (CCPH) conducted an epidemiologic investigation of 20 potentially exposed close contacts and 734 direct-care dental patients in Results. Of 20 close contacts, one family member and two coworkers, all of whom were from countries in which TB is endemic, had latent TB infection (LTBI). One U.S.-born coworker experienced a tuberculin skin test (TST) conversion from 0 to 8 millimeters. Of the 305 of 731 (41.7 percent) potentially exposed patients who received a single TST, 23 (7.5 percent) had a positive TST result of at least 5 mm. Among the subset of 157 patients tested by CCPH staff, 16 (10.2 percent) had a positive TST result. The dental office did not have infection prevention and control policies related to TB identification, prevention or education. Conclusions. The coworker s TST conversion indicated a recent infection, likely owed to occupational transmission. The proportion of dental patients with positive TST results was greater than the National Health and Nutrition Examination Survey prevalence estimate in the general population, and it may reflect transmission from the hygienist with active TB or a prevalence of LTBI in the community. Practical Implications. All dental practices should implement administrative procedures for TB identification and control as described in this article, even if none of their patients are known to have TB. Key Words. Mycobacterium tuberculosis; infection prevention and control; contact investigation; dental office; occupational infection; delayed diagnosis. JADA 2014;145(5): doi: /jada JADA 145(5) May 2014

2 health care professionals might work, including dental settings. 1 A decrease in the reports of TB outbreaks in health care settings and health care associated transmission of TB to patients and health care workers resulted after the introduction of the 1994 infection control guidelines. 1 Risk of transmission in dental settings generally is considered to be low, because few dental health care personnel (DHCP) or patients in the United States would be expected to have TB. Two published reports have documented transmission of M. tuberculosis in dental care settings. 4,5 The authors of the first report confirmed that, although unusual, transmission from an infectious health care provider or patient can occur even when the duration of exposure is no more than an hour (compared with weeks or months). 4 They reported that in 1979 and 1980, a dentist in the United Kingdom transmitted intraoral and pulmonary M. tuberculosis to 15 patients, each of whom had only a single, short exposure to the dentist while undergoing tooth extraction at two school dental clinics. 4 In 1995, a U.S. hospital-based dental clinic reported finding genetically matching isolates of multidrug-resistant M. tuberculosis (MDR TB) in two immunocompromised DHCP. 5 In that setting, a patient might have transmitted MDR TB to both DHCP, or an unknown source might have transmitted TB to one DHCP who then might have transmitted it to the other DHCP. In this article, we describe an investigation of the case of a dental hygienist who developed pulmonary TB, worked for several months while infectious and likely transmitted M. tuberculosis in a dental setting. CASE REPORT: INDEX CASE In 2010, a female dental hygienist (Hygienist A) in her mid-40s who was employed in a dental practice with 19 other people in Washington state developed active pulmonary TB disease. Born in a country endemic for TB, she had been living in the United States for more than 20 years. In March 2010, she developed a cough, fever and fatigue and sought medical evaluation from a local private health care provider. The clinician concluded that the symptoms were allergy related. Although Hygienist A continued to have symptoms, including weight loss, she continued to work, occasionally seeking care from her private health care provider. In late July, significant weight loss and fatigue finally prevented her from working and she sought medical care from a second private health care provider. At this visit, her chest radiograph revealed noncavitary bilateral pulmonary infiltrates most confluent in the right upper lobe, consistent with pulmonary TB. In addition, a sputum sample was 4+ smearpositive for acid-fast bacilli, a tuberculin skin test (TST) result was positive at 15 millimeters and a sputum culture was positive for a drug-susceptible M. tuberculosis. In August 2010, the second private health care provider reported the case to Clark County Public Health (CCPH) in Vancouver, Wash. Hygienist A s medical history included a positive TST result indicating LTBI around the time of her immigration to the United States. However, she never was offered treatment for LTBI and had no history of active TB disease. Hygienist A lived with one family member, her mother, who had been hospitalized for active TB in the 1970s. Hygienist A had no other known risk factors for TB such as diabetes, human immunodeficiency virus infection or possible exposures through a history of drug use, incarceration or homelessness. Given the clinical evaluation, which revealed a high likelihood of infectiousness, and given that Hygienist A had had close contact with patients and health care staff within a dental office for at least several months while symptomatic, CCPH conducted an epidemiologic investigation. The investigation included identification of potentially exposed contacts, evaluation of these contacts and recommendations for treatment and followup. Figure 1 illustrates the timeline from symptom onset through the investigation. METHODS Exposure. On the basis of CDC s Guidelines for Preventing the Transmission of Mycobacterium tuberculosis in Health-care Settings, 2005, 1 CCPH considered the infectious period as having begun in January 2010, three months before symptom onset, and as having continued through July 2010, when Hygienist A stopped working. We defined exposure on the basis of the time a person spent with Hygienist A, either at home or in the dental office, and we considered close contacts as exposed coworkers and a household member with frequent and prolonged contact interaction with Hygienist A over several months. We decided that the investigation would be expanded to include direct-care patients, who had less exposure, if evidence of transmission was found in any close contact. Even though Hygienist A was wearing a surgical face mask, we considered direct-care patients as being exposed because results from several studies (summarized by the National Institute for Occupational Safety and Health 6 ) showed that surgical masks do not provide adequate protection in filtering out the M. tuberculosis organism. Study population and exposure outcome definition. The study population included 754 people potentially exposed to Hygienist A. This included close contacts, ABBREVIATION KEY. CCPH: Clark County Public Health. CDC: Centers for Disease Control and Prevention. DHCP: Dental health care personnel. LTBI: Latent tuberculosis infection. M. tuberculosis: Mycobacterium tuberculosis. MDR TB: Multidrug-resistant Mycobacterium tuberculosis. NHANES: National Health and Nutrition Examination Survey. NTCA: National Tuberculosis Controllers Association. RP: Respiratory protection. TB: Tuberculosis. TST: Tuberculin skin test. JADA 145(5) May

3 Infectious period Exposure period Begin second round of testing for coworkers whose initial test results were negative Hygienist A seeks care from a second medical provider who evaluates her for TB Begin testing of family member Decision to expand investigation Symptom onset Hygienist A seeks care from her private medical provider CCPH notified of suspected case CCPH screening clinics Jan 2010 Feb Mar Apr May Jun Jul Aug Sept Oct v Dec Jan 2011 Hygienist A stops working owing to illness Diagnosis Patients notified by letter Hygienist B experiences a conversion from negative to positive TST result Figure 1. Investigation timeline. CCPH: Clark County Public Health. TB: Tuberculosis. TST: Tuberculin skin test. specifically Hygienist A s one family member and 19 coworkers, and 734 patients to whom she provided direct care during the exposure period, January through July We defined a recent infection as an exposed close contact s having a TST conversion from 0 to 5 mm or higher. We defined a probable new TB infection among direct-care patients as an exposed contact with a single TST induration of 5 mm or higher 7 and no other risk factors. 1 Contact investigation. We reviewed national guidelines established by the National Tuberculosis Controllers Association (NTCA) and CDC for performing a TB contact investigation. 7 We administered the first rounds of TSTs during August and September 2010 to the 20 close contacts and a follow-up TST eight to 10 weeks later during October and vember 2010 for the close contacts who had initial negative TST results. Because evidence of transmission was found in a close contact, in vember 2010, we expanded the contact investigation to include the notification to 734 dental patients who received care from Hygienist A during her infectious period. We developed a letter that the dental office staff members sent to the patients informing them about their possible exposure to a person with active TB and recommending that they receive TST screening through a CCPH clinic or through their private health care providers. The recommended skin testing for patients included only one round because more than eight to 10 weeks already had passed since their last exposure to Hygienist A. Data collection. At the time of screening, 157 patients reported to CCPH clinics and completed a risk assessment questionnaire developed from the NTCA/CDC guidelines for the investigation of contacts of people with infectious TB. 7 The questionnaire included a question about the patient s country of birth. The 148 patients screened by their private health care providers did not complete risk assessment questionnaires. At the CCPH clinics, a trained public health nurse or medical assistant placed the TST, measured the TST induration and entered the results (in millimeters) and risk assessment information into a surveillance database. All patients tested at the CCPH clinics provided informed consent. For patients screened by their primary care providers, the providers submitted the results by phone, voice mail or fax. Although we preferred to receive results from providers, we accepted patients selfreported results as positive or negative even if they did not provide induration measurements. This approach was implemented as a medical measure that varies from national guidelines. For contacts with positive TST results, we offered chest radiography to rule out active TB disease and recommended treatment for LTBI. Review of dental office procedures. We interviewed the dental office manager regarding administrative procedures such as baseline TB screening and education for staff memberes (for instance, recognizing signs and symptoms of TB and work restrictions). We also interviewed the DHCP regarding infection prevention and control practices and reviewed dental office documents about TB and about general infection prevention and control. RESULTS Testing. One family member and two foreign-born coworkers, all from countries in which TB is endemic, 466 JADA 145(5) May 2014

4 had positive TST results during the first round of testing (Table 1). Seventeen U.S.-born coworkers had negative TST results in the first test and underwent testing again eight to 10 weeks later. Sixteen of these 17 coworkers had negative TST results on retesting. One coworker (5.9 percent), a dental hygienist (Hygienist B) with no other known risk factors, had a TST result of 0 mm in August and a positive result of 8 mm in October. Chest radiographs were negative for TB disease. We provided treatment for LTBI to Hygienist B. The overall prevalence of LTBI among the 20 close contacts was 20 percent. Among the 734 patients potentially exposed to TB through Hygienist A, three patients with documented positive results on a previous skin test did not undergo TST. Instead, we referred them to their health care providers for clinical evaluation, including chest radiography; 305 of the remaining 731 (41.7 percent) patients, who did not have documented previous TSTs, reported to a CCPH screening clinic or private health care provider to obtain TSTs. Among the 305 patients who received a single TST, 23 (7.5 percent) had a positive TST result of 5 mm or higher, and the results for 21 of those 23 were 10 mm or higher. The prevalence of a positive TST result among patients with known country of birth was seven (5.0 percent) of 140 among U.S.-born patients and 16 (57.1 percent) of 28 among foreign-born patients. Data regarding country of birth were missing for 45 percent of patients tested, and none of these reported a positive TST result. Among the subset of 157 patients who received TSTs at a CCPH clinic, 16 (10.2 percent) had a positive TST result. Five (3.8 percent) of these were U.S. born; 11 (45.8 percent) were foreign born, all in countries in which TB is more common than in the United States: Mexico, El Salvador, Guatemala, Vietnam, Tibet and Japan (Table 2). We ordered chest radiography for all patients with positive TST results to rule out active TB disease, and we referred those with negative findings on chest radiographs to a CCPH clinic or their providers for treatment of LTBI. Dental office procedures. The dental clinic had no personnel policies or administrative procedures in place for baseline TB screening or education. DHCP, including Hygienist A, reported adhering to the clinic s policy of wearing a surgical face mask while treating patients. However, Hygienist A changed her face mask infrequently during each day and spent about one hour treating each patient. She did not wear a face mask at other times in the office, including during breaks or when she greeted or dismissed patients. TABLE 1 Positive tuberculin skin test (TST) results among Hygienist A s family members and coworkers (n = 20), according to foreign-born status. PEOPLE TESTED, ACCORDING TO FOREIGN-BORN STATUS DISCUSSION NO. SCREENED NO. (PERCENTAGE OF TOTAL) WITH POSITIVE TST RESULT U.S. born* 17 1 (5.9) Foreign born 3 3 (100) TOTAL 20 4 (20) * These patients were born in one of the 50 United States or Washington. These patients originated from the following countries: Mexico, El Salvador, Guatemala, Vietnam, Tibet and Japan. TABLE 2 Positive tuberculin skin test (TST) results among dental patients screened by CCPH* (n = 157), according to foreign-born status. PATIENTS TESTED, ACCORDING TO FOREIGN-BORN STATUS NO. SCREENED NO. (PERCENTAGE OF TOTAL) WITH POSITIVE TEST RESULT U.S. born (3.8) Foreign born (45.8) Unknown 3 0 (0) TOTAL (10.2) * CCPH: Clark County Public Health. These patients were born in one of the 50 United States or Washington. These patients originated from the following countries: Mexico, El Salvador, Guatemala, Vietnam, Tibet and Japan. Our investigation indicated that Hygienist A likely transmitted M. tuberculosis in a dental office setting to a coworker. In contact investigations, a TST reaction change from 0 to 5 mm or higher is considered to be a recent infection and not an immunologically enhanced response from a past infection (a phenomenon known as boosting ). 7 Because Hygienist B had no known risk factors for TB, her skin test conversion of 8 mm after exposure suggests that occupational transmission likely occurred. The definitive measure of TB transmission is when an exposed person develops active disease that allows for confirmation testing of culture isolates to demonstrate matching genotypes. In this case, Hygienist B s evaluation was negative for active TB. The prevalence of infection, on the basis of results of a single TST in our CCPH study population, was about 10 percent. Without baseline test results, however, a single TST result does not medically confirm new infections in patients. In addition, the prevalence of LTBI in the community or state is unknown, because skin test reactivity (or LTBI) is not what is called a notifiable infectious condition (a condition involving a legal requirement to JADA 145(5) May

5 BOX Tuberculosis (TB) infection prevention and control plan for dental health care settings. In certain settings, dental health care may be provided as part of inpatient services. If so, follow the recommendations for inpatient settings for patient rooms. ADMINISTRATIVE CONTROLS FOR DENTAL HEALTH CARE PERSONNEL (DHCP) AND PATIENTS dassign responsibility for managing the TB infection prevention and control program dconduct initial and annual risk assessment dprovide DHCP with initial and annual training regarding signs and symptoms of TB and risk of transmission dwhen hiring DHCP, ensure that they are screened for latent TB infection with a symptom screen and test for TB infection, if indicated ddevelop written TB infection prevention and control policies to identify DHCP with symptoms of TB disease and to ensure prompt medical evaluation dinclude in a patient s medical assessment, both initially and at periodic updates, documentation of symptoms or signs of TB disease or recent exposure ddevelop written TB infection prevention and control policies for promptly identifying and isolating patients with suspected or confirmed TB disease when they require urgent dental treatment; postpone nonurgent dental treatment for people who have confirmed or possible TB dinstruct coughing patients to cover their mouths when coughing or to wear a surgical mask as part of respiratory hygiene and cough etiquette procedures ENVIRONMENTAL CONTROLS FOR PATIENTS duse an airborne infection isolation room to provide urgent dental treatment to patients with suspected or confirmed infectious TB din settings with a high volume of patients with suspected or confirmed TB, consider using high-efficiency particulate air filtration or ultraviolet germicidal irradiation RESPIRATORY PROTECTION (RP) CONTROLS FOR DHCP densure that all health care settings in which health care workers evaluate or treat patients with suspected or confirmed TB disease have an RP program; an RP program might not be necessary for settings in which patients with TB disease are not encountered or in which a procedure exists for the prompt transfer of patients with suspected or confirmed TB disease to a setting with environmental controls in which they can be evaluated densure that an RP plan includes annual respirator training, initial respirator fit testing and periodic respirator fit testing ddetermine which DHCP need to be included in the RP program drequire that DHCP use RP at least an N95 particulate filter respirator (disposable filtering facepiece) that has been certified by the National Institute for Occupational Safety and Health when they are providing urgent dental treatment to patients with suspected or confirmed TB disease * Adapted from Cleveland and colleagues. 14 report it to government authorities). Estimates of the preva lence of TB infection in the U.S. population are available from the results of the National Health and Nutrition Examination Survey (NHANES), a cross-sectional, nationally representative survey. 8 NHANES investigators used a TST result of 10 mm or higher to estimate that the total prevalence of LTBI in the United States was 4.2 percent, with notably higher preva lence among foreign-born (18.7 percent) versus U.S.-born (1.8 percent) people. 8 We used a lower threshold ( 5 mm) than did NHANES investigators to define a positive TST result, although 21 of 23 people with a positive result had an induration greater than 10 mm. In comparison, the prevalence estimates of positive TST results among the 157 dental patients who underwent skin tests at a CCPH clinic were more than two times higher overall and among both foreign-born (45.8 percent) and U.S.-born (3.8 percent) patients. This difference might indicate transmission from Hygienist A to her patients or merely might reflect the prevalence of TB infection among the community population. In 2010, of the 9,666 reported TB cases among people 15 years or older who identified an occupation, 396 (4.1 percent) were health care workers and, of those, 278 (70 percent) were foreign born. 2,6 Depending on where they work, country of birth and other risk factors they might have for TB exposure, health care personnel may be at increased risk of developing LTBI, thereby posing a potential threat to patients, staff or the community if the infection evolves into active disease and if early detection, containment and treatment strategies are not implemented. 9 Like other health care facilities, dental practices may employ staff members and treat patients with risk factors for TB exposure. Although TB rates and cases have continued to decline among U.S.-born and foreign-born people now residing in the United States, new TB infections and reactivation of LTBI among these residents are 12 times higher among foreign-born people than among U.S.-born people. 10 Most people who have LTBI never develop active TB; however, up to 10 percent of people with untreated LTBI will develop active disease over the span of a lifetime. 1 In a 2012 survey of dentist owners in private practice, almost 80 percent of dentists reported having a staff member identified as an infection control coordinator in their primary practices. 11 Although DHCP routinely implement infection prevention and control practices, it is unknown how dentists have implemented recommendations specifically to prevent transmission of M. tuberculosis among patients or DHCP. 1,12,13,14 A review of dental office documents and employee 468 JADA 145(5) May 2014

6 interviews in this case revealed that the dental practice lacked CDCrecommended administrative procedures for documenting employee health immunization and screening histories such as baseline skin testing for TB infection. Therefore, the practice had not identified that Hygienist A was infected with TB, had not been treated when LTBI was first diagnosed and was at risk of developing active TB. In addition, there were no records documenting whether dental staff members received baseline education about recognizing the signs and symptoms of TB. A suggested component of initial TB training and education is to define a joint responsibility of DHCP and employers to ensure prompt medical evaluation for DHCP who develop symptoms or signs of TB disease. 1,12 The responsibility and policies for determining that DHCP with TB disease are not infectious when performing or returning to patient care have been established. 1 It is possible that such documentation could have increased suspicion of active TB once Hygienist A developed symptoms, which could have led to an earlier referral and diagnosis by a medical care provider, as well as work-restriction procedures to minimize the likelihood that her disease was infectious when she returned to work. Although study results have shown that surgical masks do not provide adequate protection against FIGURE 2 Dental Personnel Health: Annual Tuberculosis (TB) Risk Assessment Worksheet. Date of Assessment: Does the dental health care setting have a written TB infection prevention and control plan? When was the TB infection prevention and control plan last reviewed or updated? Who is responsible for the infection prevention and control program? Have all dental health care personnel (DHCP) received annual/refresher TB training and education regarding clinical TB information, immunocompromising conditions, office infection prevention and control practices, epidemiology and the role of public health? Does the dental office have a TB screening program for DHCP? If yes, which DHCP are included in the TB screening program? (Check all that apply.) Is baseline skin testing performed for all newly hired DHCP with a two-step tuberculin skin test (TST) or one blood assay for Mycobacterium tuberculosis (unless they have documentation of either a positive TST result or treat ment for latent TB infection [LTBI] or TB disease)? If no, is there a written record of a negative result for a two-step TST? If no, has baseline testing been performed with a blood assay for M. tuberculosis? For DHCP who have positive test results for M. tuberculosis infection, are efforts made to communicate test results and recommend followup of LTBI clinical evaluation with the local health department or their primary physician? On the basis of the number of TB patients encountered in one year, what is the risk classification* for your dental setting? Where are the M. tuberculosis infection test Location: records maintained for DHCP? Figure 2. Annual tuberculosis (TB) risk assessment worksheet for dental personnel. * A TB risk classification is based on the annual number of dental patients with TB disease who were evaluated and on whether the setting serves a high-risk population (see for a description of risk factors). The classification of low risk should be applied to dental health care settings in which people with TB disease are not expected to be encountered and, therefore, in which exposure to Mycobacterium tuberculosis is unlikely. Thus, if fewer than three patients with TB have been encountered in the preceding year, the risk should be classified as low. If three or more patients have been encountered in the preceding year, the risk should be classified as medium. Also, dental settings that serve communities with a high incidence of TB disease, treat populations at high risk (such as people who are homeless, are incarcerated, use injection drugs, were born outside the United States or have human immunodeficiency virus infection or other immunocompromising conditions) or treat patients with drug-resistant TB disease might need to be classified as medium risk, even if they meet the low-risk criteria. Adapted from Jensen and colleagues. 1 M. tuberculosis, 6 airborne dissemination in this case possibly was limited because Hygienist A reported wearing a surgical face mask while treating patients. 15 On the other Date: Name: If, date of annual/refresher training: Dentists Dental hygienists (or other midlevel practitioners) Dental assistants (or other auxiliary staff members) Dental technicians Administrators Receptionists Janitorial staff members Maintenance or engineering staff members Trainees and students Volunteers Others 0-2 TB patients: Low risk baseline TST testing 3 TB patients: Medium risk baseline and annual TST testing Risk assessment date: JADA 145(5) May

7 hand, Hygienist A reported that she did not change the face mask before treating each patient a practice that is inconsistent with CDC dental infection control guidelines for DHCP s personal protective equipment use. 12 Whether Hygienist A s reuse of the mask interfered with gross filtration of large droplets or had any other effect on the risk of aerosol transmission of TB is unknown. Although patients and DHCP shared the same air space for varying times, we were unable to evaluate the characteristics of exposures for specific patients or coworkers because retrospective staffing patterns were not available. This study s results highlight the importance of ensuring that appropriate infection prevention and control measures are in place in dental care settings, including a written TB infection prevention and control plan, a person or people responsible for the plan, annual risk assessments for the setting, a procedure for screening and educating workers on hiring, written work restrictions and proper use of personal protective equipment. These control measures are based on a three-level hierarchy: administrative controls, environmental controls and respiratory protection controls (Box). 1,12,14 CDC recommends that all health care settings, including dental settings, implement a TB screening program for employees and classify the setting s risk to determine the frequency of screening as outlined in Figure 2. 1 Baseline TST screening for employees can be performed in local public health departments or by private medical care providers. Regardless of risk classification, CDC recommends that all health care settings develop a written TB infection prevention and control plan and incorporate TB screening into the hiring process. 1 TB training and education also are important components of a TB screening program. 1 Limitations. Readers should consider several limitations when interpreting these findings. Among the 734 patients exposed at the dental clinic, only 305 (41.7 percent) were screened for M. tuberculosis infection. It is possible that the patients screened were not representative of all patients exposed during the infectious period. Because we were unable to validate patient reports, patients self-reported TST results might have resulted in a biased estimate. Patients might have misinterpreted test results provided by their health care providers or might have chosen not to report the results to public health officials. In addition, physicians without experience in screening for TB and reading TST results might have misclassified some patients. CONCLUSIONS Hygienist B s conversion after her exposure to an infectious coworker indicates that occupational transmission to Hygienist B likely occurred. Positive TST results among patients treated by Hygienist A could reflect prevalence of infection in the community, especially among foreign-born people from countries in which TB is endemic, but also might indicate that transmission to one or more patients occurred. The findings of this investigation highlight the need for professionals in dental care settings to examine their infection prevention and control practices to prevent transmission of TB and, if necessary, make changes to ensure that they follow CDC recommendations to protect both patients and DHCP. Dental office infection prevention and control programs should ensure prompt treatment of DHCP or patients with symptoms consistent with TB disease. It is essential that public health officials, medical care providers and dental care providers work together to prevent and control the transmission of M. tuberculosis and other infectious diseases in dental settings. Ms. Merte was a Centers for Disease Control and Prevention/Council of State and Territorial Epidemiologists Applied Epidemiology Fellow, Clark County Public Health, Vancouver, Wash., when this article was written. She now is a public health analyst, U.S. Public Health Service, Washington, D.C. Ms. Kroll was the manager, Communicable Disease Program, Clark County Public Health, Vancouver, Wash., when this article was written. She now is an infection preventionist, PeaceHealth Southwest Medical Center, Vancouver, Wash. Ms. Collins is an epidemiologist, Division of Oral Health, National Center for Chronic Disease Prevention and Health Promotion, Centers for Disease Control and Prevention, Atlanta. Dr. Melnick is the director/health officer, Clark County Public Health, Vancouver, Wash., and an adjunct associate professor, Oregon Health & Science University, Portland, Ore. Address correspondence to Dr. Melnick at Clark County Public Health, 1601 E. Fourth Plain Blvd., P.O. Box 9825, Vancouver, Wash , Alan.Melnick@clark.wa.gov. Disclosure. ne of the authors reported any disclosures. This study was supported in part by the appointment of Jennifer Merte to the Applied Epidemiology Fellowship Program administered by the Council of State and Territorial Epidemiologists and funded by the U.S. Centers for Disease Control and Prevention Cooperative Agreement 5U38HM The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the U.S. Centers for Disease Control and Prevention. The authors thank staff members at Clark County Public Health, Vancouver, Wash., who contributed to this investigation, specifically the staff of the Communicable Disease Unit, the tuberculosis program staff, and Adele Cravey, case manager. The authors also thank Lauren Lambert, Division of Tuberculosis Elimination, U.S. Centers for Disease Control and Prevention, Atlanta, for her thoughtful review of the manuscript of this article. 1. Jensen PA, Lambert LA, Iademarco MF, Ridzon R; Centers for Disease Control and Prevention. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care settings, MMWR Recomm Rep 2005;54(RR-17): Centers for Disease Control and Prevention. Reported tuberculosis in the United States, htm. Accessed Feb. 18, Centers for Disease Control and Prevention. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities, MMWR Recomm Rep 1994;43(RR-13): Smith WH, Davies D, Mason KD, Onions JP. Intraoral and pulmonary tuberculosis following dental treatment. Lancet 1982;1(8276): Cleveland JL, Kent J, Gooch BF, et al. Multidrug-resistant Mycobacterium tuberculosis in an HIV dental clinic. Infect Control Hosp Epidemiol 1995;16(1): JADA 145(5) May 2014

8 6. National Institute for Occupational Safety and Health. TB Respiratory Protection Program in Health Care Facilities: Administrator s Guide. Cincinnati: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health; 1999: National Tuberculosis Controllers Association; Centers for Disease Control and Prevention (CDC). Guidelines for the investigation of contacts of persons with infectious tuberculosis: recommendations from the National Tuberculosis Controllers Association and CDC. MMWR Recomm Rep 2005;54(RR-15): Bennett DE, Courval JM, Onorato I, et al. Prevalence of tuberculosis infection in the United States population: the National Health and Nutrition Examination Survey, Am J Respir Crit Care Med 2008;177(3): Lambert LA, Pratt RH, Armstrong LR, Haddad MB. Tuberculosis among healthcare workers, United States, Infect Control Hosp Epidemiol 2012;33(11): Centers for Disease Control and Prevention. Trends in tuberculosis: United States, MMWR Morb Mortal Wkly Rep 2012;61(11): Cleveland JL, Bonito AJ, Corley TJ, et al. Advancing infection control in dental care settings: factors associated with dentists implementation of guidelines from the Centers for Disease Control and Prevention. JADA 2012;143(10): Kohn WG, Collins AS, Cleveland JL, Harte JA, Eklund KJ, Malvitz DM; Centers for Disease Control and Prevention. Guidelines for infection control in dental health-care settings, MMWR Recomm Rep 2003;52(RR-17): Sterling TR, Haas DW. Transmission of Mycobacterium tuberculosis from health care workers. N Engl J Med 2006;355(2): Cleveland JL, Robison VA, Panlilio AL. Tuberculosis epidemiology, diagnosis and infection control recommendations for dental settings: an update on the Centers for Disease Control and Prevention guidelines. JADA 2009;140(9): Dharmadhikari AS, Mphahlele M, Stolz A, et al. Surgical face masks worn by patients with multidrug-resistant tuberculosis: impact on infectivity of air on a hospital ward. Am J Respir Crit Care Med 2012;185(10): JADA 145(5) May