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An explanation for the low proportion of tuberculosis that results from transmission between household and known social contacts

Published on Dec 1, 2018in Scientific Reports4.011
· DOI :10.1038/s41598-018-23797-2
Nicky McCreesh13
Estimated H-index: 13
(Lond: University of London),
Richard G. White39
Estimated H-index: 39
(Lond: University of London)
Abstract
We currently have little idea where Mycobacterium tuberculosis (Mtb) transmission occurs in high incidence settings. Molecular studies suggest that only around 8-19% of transmission to adults occurs within-household, or between known social-contacts. This contrasts with findings from social-contact studies, which show that substantial proportions of contact time occur in households, workplaces and schools. A mathematical model of social-contact behaviour and Mtb transmission was developed, incorporating variation in susceptibility and infectiousness. Three types of contact were simulated: household, repeated (individuals outside household contacted repeatedly with daily-monthly frequency) and non-repeated. The model was parameterised using data from Cape Town, South Africa, on mean and variance in contact numbers and contact durations, by contact type, and fitted to an estimate of overdispersion in numbers of secondary cases ('superspreading') in Cape Town. Household, repeated, and non-repeated contacts contributed 36%, 13%, and 51% of contact time, and 13%, 8%, and 79% of disease, respectively. Results suggest contact saturation, exacerbated by long disease durations and superspreading, cause the high proportion of transmission between non-repeated contacts. Household and social-contact tracing is therefore unlikely to reach most tuberculosis cases. A better understanding of transmission locations, and methods to identify superspreaders, are urgently required to improve tuberculosis prevention strategies.
  • References (22)
  • Citations (4)
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References22
Newest
#1Diya SurieH-Index: 2
#2Othusitse FaneH-Index: 1
Last. John E. OeltmannH-Index: 15
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3 CitationsSource
#1Nicky McCreesh (Lond: University of London)H-Index: 13
#2Clare Looker (Lond: University of London)H-Index: 3
Last. Richard G. White (Lond: University of London)H-Index: 39
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Background In high incidence settings, the majority of Mycobacterium tuberculosis (M.tb) transmission occurs outside the household. Little is known about where people’s indoor contacts occur outside the household, and how this differs between different settings. We estimate the number of contact hours that occur between adults and adult/youths and children in different building types in urban areas in Western Cape, South Africa, and Zambia.
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#1Peter J. DoddH-Index: 17
#2Clare LookerH-Index: 3
Last. Richard G. WhiteH-Index: 39
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We aimed to model the incidence of infection with Mycobacterium tuberculosis among adults using data on infection incidence in children, disease prevalence in adults, and social contact patterns. We conducted a cross-sectional face-to-face survey of adults in 2011, enumerating “close” (shared conversation) and “casual” (shared indoor space) social contacts in 16 Zambian communities and 8 South African communities. We modeled the incidence of M. tuberculosis infection in all age groups using thes...
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#2Linda-Gail Bekker (UCT: University of Cape Town)H-Index: 70
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Background Tuberculosis (TB) transmission rates are exceptionally high in endemic TB settings. Adolescence represents a period of increasing TB infection and disease but little is known as to where adolescents acquire TB infection. We explored the relationship between residential exposure to adult TB cases and infection in children and adolescents in a South African community with high burdens of TB and HIV.
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