Tuberculosis Outbreak Investigations in the United States, 2002–2008

Abstract

To understand circumstances of tuberculosis transmission that strain public health resources, we systematically reviewed Centers for Disease Control and Prevention (CDC) staff reports of US outbreaks in which CDC participated during 2002–2008 that involved >3 culture-confirmed tuberculosis cases linked by genotype and epidemiology. Twenty-seven outbreaks, representing 398 patients, were reviewed. Twenty-four of the 27 outbreaks involved primarily US-born patients; substance abuse was another predominant feature of outbreaks. Prolonged infectiousness because of provider- and patient-related factors was common. In 17 outbreaks, a drug house was a notable contributing factor. The most frequently documented intervention to control the outbreak was prioritizing contacts according to risk for infection and disease progression to ensure that the highest risk contacts were completely evaluated. US-born persons with reported substance abuse most strongly characterized the tuberculosis outbreaks in this review. Substance abuse remains one of the greatest challenges to controlling tuberculosis transmission in the United States.

Beijing Sublineages of Mycobacterium tuberculosis Differ in Pathogenicity in the Guinea Pig

“…Each of the sublineages had specific mutations that, based on their SIFT values, suggested an impact on gene function. The strains from sublineage RD207 had a mutation in Rv0989c (grcC2), a diphosphate synthase required for cell wall biosynthesis (27). These strains also had a mutation in the gene Rv2959c, encoding a methyltransferase involved in the biosynthesis of phenolglycolipid, which is considered a virulence factor (39).…”

“…Although some of these mutations may explain the pathological and immunological differences observed, there are a multitude of factors that can influence the transmission and pathogenic capabilities of a given isolate, such as host and environmental factors (5,20,27,38), HIV coinfection (42), and the concentration of organisms in environmental air (17). Until recently, the only bacterial factor considered was the presence of drug resistance; some studies have suggested that M. tuberculosis resistant to isoniazid is less transmissible (52) and less pathogenic than fully susceptible organisms (7,11), although an earlier study in our laboratory (33) investigating the virulence of multidrug-resistant isolates did not show much evidence of loss of virulence of these strains.…”

Using tuberculosis patient characteristics to predict future cases with matching genotype results

“…We believe this is because foreign-born children with TB who are living in the United States most likely acquired their infection before immigration to the United States, and if the source of their infection is still overseas it would not be captured in the NTSS. While index cases may not always be source cases, our findings are similar to those from studies that assessed risk factors for genotype clustering, 6 recent transmission 7 and involvement in outbreaks, 8 reinforcing the notion that index cases characterized by these risk factors may often be the source case for future cases. We found only one study that assessed characteristics associated with the generation of secondary cases using epidemiologic but not genotyping data.…”

A Tuberculosis Outbreak Fueled by Cross-Border Travel and Illicit Substances: Nevada and Arizona

“…5,24 The index patient's prolonged infectious period, resulting primarily from treatment nonadherence but also a delay in seeking medical care, was the main factor that fueled this outbreak. Delayed diagnosis is a wellknown risk factor for TB transmission, 14,25 and it has previously contributed to at least two known TB outbreaks involving undocumented people. 26,27 Undocumented foreign-born people are more likely than documented people to delay seeking care for symptoms, 28 thereby prolonging the infectious period when TB can be transmitted to others.…”

“…13 To prevent further cases, exposed people with pending or incomplete TB evaluation and LTBI treatment were classified into high, medium, and low priority for follow-up based on the presence of TB risk factors, extent of exposure (i.e., intensity, duration, and frequency), and risk of developing TB disease. 13,14 Additional contacts identified during the outbreak investigation interviews and chart reviews were added to the database and prioritized for evaluation.…”