CDC Logo Tuberculosis Information CD-ROM   Image of people
jump over main navigation bar to content area
TB Guidelines
Surveillance Reports
Slide Sets
TB-Related MMWRs and Reports
Education/Training Materials
Ordering Information


U.S. Department of Health and Human Services


This is an archived document. The links are no longer being updated.

TB Notes 2, 2004


Year in Review: TB Outbreak Investigations 2003

Like the previous year, 2003 was a busy year for the Outbreak Investigations Team (OIT) in DTBE’s Surveillance, Epidemiology, and Outbreak Investigations Branch (SEOIB). During 2003, DTBE’s Outbreak Evaluation Unit received 34 reports of TB outbreak activity. In response to these, at the local jurisdictions’ request, the OIT conducted six on-site Epi-Aid investigations (five national and one international) and provided technical assistance in response to three other reports. The Field Services and Evaluation Branch (FSEB), the Communications, Education, and Behavioral Studies Branch (CEBSB), and the Clinical and Health Systems Research Branch (CHSRB) collaborated with OIT on these investigations.

The highlights of the year’s outbreak investigations were the predominant outbreak investigations among homeless persons and the use of the Quantiferon®-TB test (QFT) as part of a research protocol for detection of latent TB infection (LTBI) during large contact investigations and outbreaks.1 The results of QFT use will be described later once the study is completed and data are analyzed.

During 2003, the OIT conducted three Epi-Aid investigations among homeless persons (in Seattle, Washington; Portland, Maine; and Wichita, Kansas). Although the three situations were similar in involving homeless persons, there were differences in the demographic characteristics and risk factors among these groups that warranted the use of a variety of innovative strategies by the epi-investigation teams to conduct detailed and thorough contact investigations.

The first of these investigations was conducted during May 2002 – September 2003 in Seattle, Washington, where Public Health – Seattle-King County (PH-SKC) found 44 persons with outbreak-associated TB. All but three of the outbreak-associated patients were homeless at the time of diagnosis; 43 (98%) were born in the United States, 34 (77%) were male, 21 (48%) were American Indian or Alaska Native, and 17 (39%) were black. Of the 38 (86%) persons with pulmonary disease, 23 (61%) had acid-fast bacilli detected on sputum smear at diagnosis. Seven (16%) outbreak-associated patients were also infected with human immunodeficiency virus (HIV). In January 2003, a CDC Epi-Aid team, along with PH-SKC, assisted in finding contacts at highest risk for exposure. Investigators reinterviewed outbreak patients and health care providers serving homeless facilities to find additional patient contacts. Sites of transmission were determined by review of homeless facility intake registries for the presence of persons with infectious TB disease and the rates of positive tuberculin skin test (TST) results among staff and clients. Exposed cohorts were found at three sites of transmission. The cohort prioritized for intensive testing included 385 contacts from three homeless facilities and 86 other contacts named by patients or health care providers. In February 2003, PH-SKC began an intensive effort to test the high-priority cohort for TB disease and LTBI in the TB clinic and at homeless facilities; this included symptom review, chest radiograph, sputum examination and culture, TST, and voluntary HIV counseling and testing. During February–September 2003, approximately 380 contacts were screened with chest radiograph or sputum culture or both. Of the 44 outbreak-associated patients, 20 were reported during this time, and 11 (55%) were found through these intensive and focused screening efforts, limiting the amount of time these persons were exposing others in the community.2

The second investigation was conducted in Portland, Maine, which is a low-incidence state. During June 2002 – July 2003, seven men with pulmonary TB disease in Portland, Maine, were reported to the Maine Bureau of Health (MBH). Six were linked through residence at homeless shelters; four had matching genotypes. As of November 20, 2003, the investigation had found 1,069 contacts, 36 (3%) of whom reported having a positive TST result previously. Among the 1,033 persons eligible for a TST, 648 (63%) received at least one test, and 56 (9%) of these had a positive result; 15 (27%) of the 56 are receiving, and one completed, therapy for LTBI. A total of 163 (15%) contacts had chest radiographs; no additional active cases were detected. Delayed diagnosis and missed opportunities for TB prevention were determined to be major contributors for TB transmission. Prompt investigation and identification of contacts likely prevented further spread of TB.3

The third investigation was conducted in Sedgwick County, Kansas, where in 2003, TB genotyping detected a potential five-case cluster.  Traditional name-based TB contact investigations had not revealed epidemiologic links. An Epi-Aid team conducted a targeted investigation in collaboration with the Sedgwick County health department to determine location-based links and the extent of transmission, and recommend TB control measures. Medical records were reviewed to determine TB patients’ infectious periods, followed by reinterviews about their activities and locations while contagious. Homeless facilities’ logs were reviewed to find common stays between contagious TB patients and other facility clients. Clients were divided into exposure categories according to number of common stays. Location-based contacts received TB screening, including a TST. TB genotyping provided the impetus to investigate locations linking the patients in this cluster. The investigation determined plausible transmission sites and directed the county’s TB control strategies, which now include mandatory TB screening at all homeless facilities.

As the TB control community collectively moves towards TB elimination in the United States, it is important to remember that TB is receding back into the traditional “pockets” of infection as evidenced by the TB outbreaks among homeless persons described above. These and other high-risk, hard-to-reach populations will provide challenges to all of us. We should remain vigilant and closely monitor TB control efforts, especially in population groups at high risk for TB. Moreover, we all face the additional challenge of reduced public health resources. It is now more important than ever for public health organizations at the local, state, and national levels to continue to work closely together against TB. Health departments may request DTBE assistance with outbreaks, cluster investigations, or other instances of TB transmission by contacting their DTBE Program Consultant. Such assistance may take the form of programmatic consultation, technical assistance, or on-site assistance (for example, an Epi-Aid). Your partners in DTBE are eager to work with you to achieve our common goal of TB elimination.

—Reported by Kashef Ijaz, MD, MPH
Div of TB Elimination


1. CDC. Guidelines for using the QuantiFERON®-TB test for diagnosing latent Mycobacterium tuberculosis infection. MMWR 2003; 52 (No. RR-2: [15-18]).

2. CDC. Public health dispatch: Tuberculosis outbreak among homeless persons-King County, Washington, 2002-2003. MMWR 2003; 52(49);1209-1210.

3. CDC. Public health dispatch: Tuberculosis outbreak in a homeless population-Portland, Maine, 2002-2003. MMWR 2003; 52(48);1184-1185.


Released October 2008
Centers for Disease Control and Prevention
National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention
Division of Tuberculosis Elimination -

Please send comments/suggestions/requests to:, or to
CDC/Division of Tuberculosis Elimination
Communications, Education, and Behavioral Studies Branch
1600 Clifton Rd., NE - Mailstop E-10, Atlanta, GA 30333