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TB Notes 1, 2000
Where We've Been and Where We're Going: Perspectives from CDC's Partners in TB Control
Changes I've Seen
TB Control in New York City: A Recent History
Not by DOT Alone
Baltimore at the New Millennium
From Crickets to Condoms and Beyond
The Denver TB Program: Opportunity, Creativity, Persistence, and Luck
National Jewish: The 100-Year War Against TB
Earthquakes, Population Growth, and TB in Los Angeles County
TB in Alaska
CDC and the American Lung Association/ American Thoracic Society: an Enduring Public/Private Partnership
The Unusual Suspects
The Model TB Prevention and Control Centers: History and Purpose
My Perspective on TB Control over the Past Two to Three Decades
History of the IUATLD
Thoughts about the Future of TB Control in the United States
Where We've Been and Where We're Going: Perspectives from CDC
Early History of the CDC TB Division, 1944-1985
CDC Funding for TB Prevention and Control
Managed Care and TB Control - A New Era
Early Research Activities of the TB Control Division
The First TB Drug Clinical Trials
Current TB Drug Trials: The Tuberculosis Trials Consortium (TBTC)
TB Communications and Education
TB Control in the Information Age
Field Services Activities
TB's Public Health Heroes
Infection Control Issues
A Decade of Notable TB Outbreaks: A Selected Review
International Activities
The Role of CDC's Division of Quarantine in the Fight Against TB in the U.S.
The STOP TB Initiative, A Global Partnership
Seize the Moment - Personal Reflections
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This is an archived document. The links are no longer being updated.

TB Notes 1, 2000

A Decade of Notable TB Outbreaks: A Selected Review

by Scott B. McCombs, MPH
Deputy Chief, Surveillance and Epidemiology Branch

The Surveillance and Epidemiology Branch is charged with monitoring TB morbidity and mortality in cooperation with state and local health departments. One of the most fascinating and important parts of our role is to assist our partners in responding to outbreaks of TB when they occur. This article summarizes a cross-section of some of the more notable outbreaks from the 1990s.

Extensive transmission of Mycobacterium tuberculosis from a child (Curtis, Ridzon, Vogel, et al. N Engl J Med 1999;341:1491-1495).
Although young children rarely transmit TB, infectious TB was diagnosed in a 9-year-old boy in North Dakota in July 1998. The child was screened because extrapulmonary TB was diagnosed in his female guardian. The child, who had come from the Republic of the Marshall Islands in 1996, had bilateral cavitary TB. Because he was the only known possible source of his guardian's TB, an investigation of the child's contacts was undertaken. Family, school, day-care, and other social contacts were notified of their exposure and given tuberculin skin tests (TST). Of the 276 contacts tested, 56 had a positive TST (10 mm induration), including 3 of 4 household members, 16 of his 24 classroom contacts, 10 of 32 school-bus riders, and 9 of 61 day-care contacts. A total of 118 persons received preventive therapy. The 9-year-old patient's twin brother had TB, but was deemed not infectious on the basis of a negative sputum smear. This investigation showed that children with TB, especially cavitary or laryngeal TB, should be considered infectious, and that screening of their contacts may be required.

Spread of Strain W, a highly drug-resistant strain of Mycobacterium tuberculosis, across the United States (Agerton, Valway, Blinkhorn, et al. Clin Infect Dis 1999; 29:85-92).
Strain W, a highly drug-resistant strain of Mycobacterium tuberculosis, was responsible for large nosocomial outbreaks in New York in the early 1990s. This article is a review of data from epidemiologic investigations, national TB surveillance, regional DNA fingerprinting laboratories, and the CDC Mycobacteriology Laboratory to identify potential cases of TB due to Strain W. From January 1992 through February 1997, 23 cases were identified in nine states and Puerto Rico; 4 of the 23 cases transmitted disease to 10 other people. Eighty-six contacts of the 23 cases were presumed to be infected with Strain W. The authors conclude that Strain W TB cases will occur throughout the United States as persons infected in New York move elsewhere. CDC asked health departments to notify CDC of cases of TB that were resistant to isoniazid, rifampin, streptomycin, and kanamycin. The references for this article include citations for earlier investigation results that have been published, including this next one.

Transmission of a highly drug-resistant strain (Strain W1) of Mycobacterium tuberculosis: Community outbreak and nosocomial transmission via a contaminated bronchoscope (Agerton, Valway, Gore, et al. JAMA 1997;278:1073-1077).
In 1995, eight patients with MDR TB were identified in South Carolina; all were resistant to seven drugs and had matching DNA fingerprints (Strain W1). Community links were identified for five patients (patients 1-5), but no links were identified for the other three patients (patients 6-8) except being hospitalized at the same hospital as one community patient. Patients 5 and 8 both died of MDR TB less than one month after diagnosis. Patients 6 and 7 each had one positive culture for MDR TB; specimens were collected during bronchoscopy. Patient 6 had a skin test conversion after bronchoscopy. Neither patient 6 nor patient 7 had a clinical course consistent with MDR TB, neither was treated for MDR TB, and both are alive and well. There was no evidence of laboratory contamination of specimens, transmission on wards, or contact among patients. All four received bronchoscopy in the same month. Observations revealed that bronchoscope cleaning and disinfection was inadequate and led to subsequent false-positive cultures in patients 6 and 7, transmission of infection to patient 6 and active MDR TB to patient 8.

>An outbreak involving extensive transmission of a virulent strain of Mycobacterium tuberculosis (Valway, Sanchez, Shinnick, et al. N Engl J Med 1998;338:633-639).
From 1994 to 1996 there was a large outbreak of TB in a small, rural community with a population at low risk for TB. Twenty-one patients with TB were identified; the DNA fingerprints of the 13 isolates available for testing were identical. To determine the extent of transmission, we investigated both the close and casual contacts of the patients. Using a mouse model, we also studied the virulence of the strain of Mycobacterium tuberculosis that caused the outbreak. The index patient, the source patient, and one other patient infected the other 18 persons. In five, active disease developed after only brief, casual exposure. There was extensive transmission from the three patients to both close and casual contacts. Of 429 contacts, 311 (72%) had positive skin tests, including 86 documented skin test conversions. The growth characteristics of the strain involved in the outbreak greatly exceeded those of other clinical isolates of M. tuberculosis. The extensive transmission of TB in this outbreak may have been due to the increased virulence of the strain rather than to environmental factors or patient characteristics.

Image 1: Figure holding a magnifying glass.

A nosocomial outbreak of multidrug- resistant tuberculosis (Kenyon, Ridzon, Luskin-Hawk, et al. Ann Intern Med 1997;127:32-36).
This article details an outbreak of seven cases of MDR TB (in six patients and one health care worker, all of whom had AIDS) that occurred in a hospital in Chicago. The hospital had a respirator fit-testing program but no acid-fast bacilli isolation rooms. All seven M. tuberculosis isolates had matching DNA fingerprints. Of patients exposed to M. tuberculosis, those who developed TB had lower CD4+ T-lymphocyte counts and were more likely to be ambulatory than those who did not. Of 74 exposed health care workers, the 11 who converted their skin tests were no more likely than those who did not convert to report that they always wore a respirator with a HEPA filter. Transmission of M. tuberculosis occurred in a hospital that did not have recommended isolation rooms. A respirator fit-testing program did not protect health care workers in this setting.

Outbreak of drug-resistant tuberculosis with second-generation transmission in a high school in California (Ridzon, Kent, Valway, et al. J Pediatr 1997;131:863-868).
In the spring of 1993 four students in a high school were diagnosed with TB resistant to isoniazid, streptomycin, and ethionamide. A retrospective cohort study with case investigation and skin test screening was conducted in the school of approximately 1,400 students. DNA fingerprinting of available isolates was performed. Eighteen students with active TB were identified. Through epidemiologic and laboratory investigation, 13 cases were linked. Nine of the 13 had positive cultures for M. tuberculosis with isoniazid, streptomycin, and ethionamide resistance, and all eight available isolates had identical DNA fingerprints. No staff member at the school had TB. One student remained infectious for 29 months and was the source case of the outbreak. Another student was infectious for 5 months before diagnosis and was a treatment failure. This student subsequently developed additional resistance to rifampin and ethambutol. The initial skin test screening found 292 of 1263 (23%) students tested had a positive TST. Risk of infection was highest among twelfth graders and classroom contacts of the two students with prolonged infectiousness. An additional 94 of 928 (10%) students tested later had a positive TST; 22 were classroom contacts of the student with treatment failure and 21 of these were documented TST conversions. This article documents extensive transmission of drug-resistant TB along with missed opportunities for prevention and control of the outbreak. Prompt identification of TB cases and timely interventions should help reduce these problems.

Transmission of multi-drug resistant Mycobacterium tuberculosis during a long airplane flight (Kenyon, Valway, Ihle, et al. N Engl J Med 1996;334:933-938).
In April 1994 a passenger with infectious MDR TB traveled on commercial-airline flights from Honolulu to Chicago and from Chicago to Baltimore and returned one month later. We sought to determine if this passenger infected any of her contacts on this extensive trip. Of 925 people on the airplanes, 802 responded to a request to complete a questionnaire and be screened by tuberculin skin test. All 11 contacts with positive TST who were on the April flights and 2 of 3 contacts with positive TST on the Baltimore-to-Chicago flight in May had other risk factors for tuberculosis. More contacts on the 8.75 hour flight from Chicago to Honolulu had a positive TST than on the other three flights. Of 15 contacts with a positive TST on the Chicago-to-Honolulu flight, six (four with skin-test conversions) had no other risk factors; all six sat in the same section as the index patient. Passengers seated within two rows of the index patient were more likely to have a positive TST than those in the rest of the section. Transmission of M. tuberculosis in this setting involved a highly infectious passenger, a long flight, and close proximity of contacts to the index patient.

The Division of TB Elimination and our partners in state and local health departments have benefitted tremendously from what has been learned from these and other outbreaks. Our continued cooperation, diligence, and timely systematic response to future outbreaks are critical to our eventual success in eliminating TB from the United States.


Released October 2008
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