Risk factors for transmission of tuberculosis among United States-born African Americans and Whites

Abstract

SUMMARY SETTING Tuberculosis (TB) patients and their contacts enrolled in nine states and the District of Columbia from 16 December 2009 to 31 March 2011. OBJECTIVE To evaluate characteristics of TB patients that are predictive of tuberculous infection in their close contacts. DESIGN The study population was enrolled from a list of eligible African-American and White TB patients from the TB registry at each site. Information about close contacts was abstracted from the standard reports of each site. RESULTS Close contacts of African-American TB patients had twice the risk of infection of contacts of White patients (adjusted risk ratio [aRR] 2.1, 95%CI 1.3–3.4). Close contacts of patients whose sputum was positive for acid-fast bacilli on sputum smear microscopy had 1.6 times the risk of tuberculous infection compared to contacts of smear-negative patients (95%CI 1.1–2.3). TB patients with longer (>3 months) estimated times to diagnosis did not have higher proportions of infected contacts (aRR 1.2, 95%CI 0.9–1.6). CONCLUSION African-American race and sputum smear positivity were predictive of tuberculous infection in close contacts. This study did not support previous findings that longer estimated time to diagnosis predicted tuberculous infection in contacts.

Strain-specific estimation of epidemic success provides insights into the transmission dynamics of tuberculosis

“…As a consistent example, short-term THD, hence short-term epidemic success, was associated with positivity of smear sputum, which is well known to impact on patient contagiousness40. Sputum positivity, which reflects disease severity4142, is thought to be linked to host-related factors, both behavioral or connected to genetic susceptibility4243, but perhaps as well to pathogen-related factors44. The general causal relationship between long-term THD and epidemic success and pulmonary forms of TB, representing the infectious form of the disease, is also straightforward.…”

Effectiveness of Canada's tuberculosis surveillance strategy in identifying immigrants at risk of developing and transmitting tuberculosis: a population-based retrospective cohort study

“…Studies of nosocomial transmissions and outbreaks also point to an association between delayed diagnosis and increased transmission. 23,24 However, longer time to diagnosis did not predict tuberculosis transmission in contacts of US-born patients with pulmonary disease 25 nor was it associated with increased transmission to close contacts of foreign-born US patients. 26 An alternative possibility is that the referral group represents a phenotypically distinct disease entity.…”

Association of Low Sputum Smear Positivity among Tuberculosis Patients with Interferon-Gamma Release Assay Outcomes of Close Contacts in Japan

“…In previous studies that did not classify patients based on sputum smear grading, contacts of patients with sputum smear positivity showed higher LTBI positivity rates than those of patients with smear negativity [2,15,16,17,18,19,20]. However, since sputum smears were not graded, these studies were unable to directly compare LTBI positivity between contacts of patients with sputum smear AFB 1+ and those of patients with smear negativity.…”