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Nosocomial transmission of mycobacterium tuberculosis found through screening for severe acute respiratory syndrome--Taipei, Taiwan, 2003.

The emergence of severe acute respiratory syndrome (SARS) has highlighted the importance of hospital infection-control programs (1). Prevention of Mycobacterium tuberculosis transmission also requires effective infection control in health-care facilities (2,3). In Taipei, Taiwan, an area with moderate to high incidence of tuberculosis (TB) (50-74 cases per 100,000 population), health-care workers (HCWs) are at increased risk for M. tuberculosis (Taiwan Center for Disease Control, unpublished data, 2002). In April 2003, SARS-related screening in a hospital in Taipei resulted in the detection of suspected TB among HCWs. This report summarizes how SARS screening led to the discovery of 60 cases of TB. HCWs in Taiwan should remain vigilant for cases of TB so persons suspected of having TB are evaluated and treated promptly.

In April 2003, an HCW being screened for SARS symptoms (e.g., fever and respiratory illness, including cough and shortness of breath) had a pleural effusion; a pleural biopsy culture grew M. tuberculosis. TB screening of close co-workers identified six additional cases of pulmonary TB, and hospital administrators implemented active case-finding. A TB case was defined by bacteriologic confirmation or diagnosis by a clinician (4). During June-July 2003, hospitalwide screening of HCWs identified 28 (2%) of 1,409 with TB.

During October-November 2003, a repeat hospitalwide screening of 1,463 HCWs identified an additional 29 cases of TB; five (17%) were later found not to have TB after reinterpretation of their chest radiographs. Another HCW with a normal chest radiograph had cervical TB lymphadenitis diagnosed during an outpatient clinic visit.

A total of 60 cases of TB among HCWs were diagnosed; 51 (85%) were in women, and median age was 30 years (range: 22-65 years). The majority of HCWs had radiologic evidence consistent with early stages of TB; 43 (72%) had pulmonary TB, five (8%) had pleural involvement only, one (2%) had TB of the cervical lymph nodes, and 11 (18%) remain unclassified. All had tested negative for human immunodeficiency virus at the time of initial hire. All were started on anti-TB therapy and continue to be monitored. As of December 3, follow-up evaluations documented that 18 HCWs had improved findings on chest radiograph, and two had stable findings; response to therapy for the remaining 40 is pending further follow-up.

Five (8%) of 59 HCWs with a pulmonary or pleural TB diagnosis reported symptoms suggestive of TB. After multiple submissions (median = three; range: one to four) of induced sputum specimens, 11 (19%) HCWs had bacteriologic evidence of TB. Of these, three (27%) had a single smear-positive result for acid-fast bacilli (AFB), seven (64%) had at least one culture that grew M. tuberculosis, and one (9%) was both smear- and culture-positive. Of the eight culture-confirmed cases, seven (88%) had isolates with matching genotypes by spoligotyping and restriction fragment length polymorphism techniques.

Review of patient records revealed that an elderly patient had spent 12 weeks on floor A (pulmonary unit) without respiratory isolation before AFB-positive pulmonary TB was diagnosed in May 2003. The patient's hospital course was complicated, eventually requiring continuous ventilator support and frequent endotracheal suctioning. Isolates from this patient matched the genotype of the seven culture-positive HCWs, five of whom (including the first diagnosed HCW) worked on floor A.

A questionnaire to determine factors associated with being diagnosed with TB during 2003 was completed by 1,555 (88%) of 1,759 full-time, part-time, volunteer, and contract HCWs, including 57 (95%) of the 60 HCWs with TB. Questions included information on personal and household exposure to TB, medical conditions and medications used, living arrangements (e.g., hospital dormitory), occupation, work locations, involvement in the care of TB patients, and presence during potential aerosol-generating clinical procedures* during January-June 2003. The majority of cases occurred among nurses (21 [4%] of 557). However, the attack rate was highest among respiratory technicians (three of seven [43%]) and radiology technicians (four [16%] of 21). HCWs on floor A had the highest attack rate (28 [36%] of 77) (Table).

Editorial Note: This report describes the need for HCW education and surveillance to prevent outbreaks of TB in healthcare facilities. In the hospital in Taipei, special SARS screenings resulted in the discovery of 60 HCWs who were diagnosed with TB and started on anti-TB therapy early during the course of illness, which potentially averted increased morbidity and further transmission.

Nosocomial transmission of M. tuberculosis among HCWs was confirmed by frequent aerosol-generating clinical procedures on a known TB patient during an extended stay on one floor, positive cultures from eight HCWs, matching genotypes from seven of these HCWs and the putative source patient, and work locations near the source patient. Work practices can be adjusted to reduce the likelihood of M. tuberculosis exposure to HCWs (2,3). For example, aerosol-generating procedures should be performed in separate ventilated areas with negative pressure (relative to adjacent areas), where all HCWs wear appropriate personal respiratory protection (2).

The majority of HCWs described in this report were considered to have TB on the basis of radiologic abnormalities. In this investigation, chest radiographs were a helpful component of active case-finding; however, TB diagnosis on the basis of chest radiograph alone, particularly in an asymptomatic person, can be unreliable, and bacteriologic confirmation should be sought for suspected cases of TB (5). For routine surveillance, radiographs are costly and inefficient because the yield usually is low. Active screening for TB-compatible symptoms, with targeted further evaluation as needed, might yield more true cases and is more cost-effective. The World Health Organization recommends that HCWs be educated about signs and symptoms of TB and instructed to report for evaluation if these develop. Consideration also should be given to establishing an HCW TB registry (2).

During 1998-2002, all specialized TB hospitals in Taiwan were closed; as a result, more cases are being managed in general hospital settings, which increases the risk for nosocomial transmission of M. tuberculosis. HCWs in Taiwan should remain vigilant for cases of TB so persons suspected of having TB are evaluated and treated promptly.
TABLE. Number of health-care workers (HCWs) surveyed * and number with
tuberculosis (TB) diagnosed, by hospital floor and unit--Taipei,
Taiwan, 2003

Floor                 Unit                No. HCWs

Floor A               Pulmonary               77
Floor B               Intensive care          57
Floor C               Radiology               84
Floor D               Dialysis               165
Remaining floors                           1,172

                       TB diagnosed
Floor                 No.        (%)

Floor A               28         (36)
Floor B                6         (11)
Floor C                4          (5)
Floor D                5          (3)
Remaining floors      14          (1)

Floor                 Odds ratio          (95% CL
                                        ([dagger]))

Floor A                  47.3           (23.4-95.4)
Floor B                   9.7            (2.9-22.0)
Floor C                   4.1            (1.6-16.8)
Floor D                   2.6             (0.9-7.2)
Remaining floors       Referent

* Only HCWs who completed the questionnaire are included.

([dagger]) Confidence limits.


* Including bronchoscopy, endotracheal intubation, respiratory suctioning, sputum induction, and nebulized treatments.

References

(1.) Lee N, Hui D, Wu A, et al. A major outbreak of severe acute respiratory syndrome in Hong Kong. N Engl J Med 2003;348:1986-94.

(2.) World Health Organization. Guidelines for the Prevention of Tuberculosis in Health Care Facilities in Resource-Limited Settings. Geneva, Switzerland: World Health Organization, 1999.

(3.) CDC. Guidelines for preventing the transmission of Mycobacterium tuberculosis in health-care facilities, 1994. MMWR 1994;43(No. RR-13).

(4.) World Health Organization. Treatment of Tuberculosis: Guidelines for National Programmes, 3rd ed. Geneva, Switzerland: World Health Organization, 2003.

(5.) Toman K. Toman's Tuberculosis: Case Detection, Treatment and Monitoring, 2nd ed. Geneva, Switzerland: World Health Organization, 2002:39-47.
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Author:Chou, M-Y.; Sun, C-C.; Yeh, P-F.; Liu, J-H.; Chen, K-T.; Chang, H.; Hung, C.J.; Wu, Y-C.; Chou, J-H.
Publication:Morbidity and Mortality Weekly Report
Geographic Code:9TAIW
Date:Apr 23, 2004
Words:1229
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