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 these contact patterns, as well as the observed incidence of M. tuberculosis infection in children and the prevalence of tuberculosis disease in adults. A total of 3,528 adults participated in the study. The reported rates of close and casual contact were 4.9 per adult per day (95% confidence interval: 4.6, 5.2) and 10.4 per adult per day (95% confidence interval: 9.3, 11.6), respectively. Rates of close contact were higher for adults in larger households and rural areas. There was preferential mixing of close contacts within age groups and within sexes. The estimated incidence of M. tuberculosis infection in adults was 1.5-6 times higher (2.5%-10% per year) than that in children. More than 50% of infections in men, women, and children were estimated to be due to contact with adult men. We conclude that estimates of infection incidence based on surveys in children might underestimate incidence in adults. Most infections may be due to contact with adult men. Treatment and control of tuberculosis in men is critical to protecting men, women, and children from tuberculosis.
Bibliographical noteFunding Information:
Author affiliations: TBModelling Group, Department of Infectious Disease Epidemiology, Faculty of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London, United Kingdom (Peter J. Dodd, Clare Looker, Ian D. Plumb, Emilia Vynnycky, Richard G. White); Health Economics and Decision Science, School of Health and Related Research, University of Sheffield, Sheffield, United Kingdom (Peter J. Dodd); Global Health and Development Department, Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, London, United Kingdom(Virginia Bond); Zambia-SouthAfrica TB andAIDS Reduction Project, School of Medicine, University of Zambia, Lusaka, Zambia (Virginia Bond, Ab Schaap, Kwame Shanaube, Monde Muyoyeta, Helen Ayles); Statistics Modelling and Economics Department, Public Health England, London, United Kingdom (Emilia Vynnycky); Department of Clinical Research, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom (Peter Godfrey-Faussett, Elizabeth L. Corbett, Helen Ayles); TB and HIV Theme, Malawi-Liverpool- Wellcome Trust Clinical Research Programme, Blantyre, Malawi (Elizabeth L. Corbett); and Desmond Tutu TB Centre, Department of Paediatrics and Child Health, Stellenbosch University, Cape Town, South Africa (Nulda Beyers). R.G.W., P.J.D., C.L., and I.D.P. were supported by the Consortium to Respond Effectively to the AIDS TB Epidemic funded by the Bill and Melinda Gates Foundation (grant 19790.01). R.G.W. was also supported by the Medical Research Council (UK) (grant G0802414), and E.L.C was supported by The Wellcome Trust (grant GR095878). We thank the Zambia AIDS Related Tuberculosis study team and Dr. Rory Dunbar, Dr. Ken Eames, Professor John Edmunds, Dr. Amelia Crampin, and Dr. Immo Kleinschmidt, all of whom contributed advice in the design and analysis of the social contact survey. We also thank the Ministry of Health, District Health Management teams and the communities at institutions where the studies were undertaken for their help and advice. The funders had no involvement in the design, collection, analysis or interpretation of the data, in writing the report or in the decision to submit.
© 2015 The Author 2015. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health.
- disease burden
- infection incidence
- social contact pattern