Tuberculosis in Household Contacts of Infectious Cases in Kampala, Uganda

Abstract

Tuberculosis remains a serious threat to public health, especially in sub-Saharan Africa. To determine the host and environmental factors responsible for tuberculosis in African households, the authors performed a prospective cohort study of 1,206 household contacts of 302 index cases with tuberculosis enrolled in Uganda between 1995 and 1999. All contacts were systematically evaluated for active tuberculosis and risk factors for active disease. Among the 1,206 household contacts, 76 secondary cases (6%) of tuberculosis were identified. Of these cases, 51 were identified in the baseline evaluation, and 25 developed during follow-up. Compared with index cases, secondary cases presented more often with minimal disease. The risk for secondary tuberculosis was greater among young children than adults (10% vs. 1.9%) and among human immunodeficiency virus-seropositive than -seronegative contacts (23% vs. 3.3%). Host risk factors could not be completely separated from the effects of environmental risk factors, suggesting that a household may represent a complex system of interacting risks for tuberculosis.

Prevalence of Latent Tuberculosis Infection among Paramedical Students in Two Hospitals in Uganda

“…The prevalence of latent TB infection in the present study is higher than in previous surveys 12,13 in Kampala, Uganda where values of 57% and 66% of TST induration ≥10 mm were reported. Kayanja et al 13 postulated that health workers from clinical departments are at greater risk for latent TB infection due to regular contact with infectious cases in the clinics and wards.…”

“…In the present study, an induration of < 10 mm was considered negative for latent TB infection (Table 2) because TB infection is endemic in Uganda 12 . Since there is strong evidence that hospital acquired TB infection is an important occupational problem among HCWs in LMICs (2) and the present respondents are expected to join the workforce shortly after graduating, their health is a matter of concern for continued health care delivery to the majority of Ugandans.…”

“…In Uganda, the prevalence of TB infection in the household contacts surveyed between 1995 and 1999 in Kampala was found to be 66% 12 . In another study among HCWs in Kampala carried out in 2001, the prevalence of latent TB infection was found to be 57% 13 .…”

Heterogeneity in tuberculosis transmission and the role of geographic hotspots in propagating epidemics

“…Such cross-transmission events may be common in the setting of nosocomial transmission, incarceration, migration/transportation, and occupational exposures. Prior studies have shown that the amount of transmission that occurs in the household may be small (21,22), but other transmission events (e.g., at social events) (23) may be far more likely to occur within geographically defined boundaries than across them. This may also be true of hotspots (e.g., townships in Cape Town, South Africa) (24) that are geographically isolated from low-incidence areas.…”

Genetic and Shared Environmental Influences on Interferon-γ Production in Response to Mycobacterium tuberculosis Antigens in a Ugandan Population

“…Study design and enrollment procedures have been described in detail elsewhere. 5,7,23 contact study of Mtb infection and TB disease conducted in Kampala, Uganda. Households were ascertained through an individual with culture-positive TB (index case).…”