Defining adequate contact for transmission of Mycobacterium tuberculosis in an African urban environment

Castellanos, María Eugenia, Zalwango, Sarah, Kakaire, Robert, Ebell, Mark H., Dobbin, Kevin K., Sekandi, Juliet, Kiwanuka, Noah, and Whalen, Christopher C. (2020) Defining adequate contact for transmission of Mycobacterium tuberculosis in an African urban environment. BMC Public Health, 20. 892.

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The risk of infection from respiratory pathogens increases according to the contact rate between the infectious case and susceptible contact, but the definition of adequate contact for transmission is not standard. In this study we aimed to identify factors that can explain the level of contact between tuberculosis cases and their social networks in an African urban environment.


This was a cross-sectional study conducted in Kampala, Uganda from 2013 to 2017. We carried out an exploratory factor analysis (EFA) in social network data from tuberculosis cases and their contacts. We evaluated the factorability of the data to EFA using the Kaiser-Meyer-Olkin Measure of Sampling Adequacy (KMO). We used principal axis factoring with oblique rotation to extract and rotate the factors, then we calculated factor scores for each using the weighted sum scores method. We assessed construct validity of the factors by associating the factors with other variables related to social mixing.


Tuberculosis cases (N = 120) listed their encounters with 1154 members of their social networks. Two factors were identified, the first named “Setting” captured 61% of the variance whereas the second, named ‘Relationship’ captured 21%. Median scores for the setting and relationship factors were 10.2 (IQR 7.0, 13.6) and 7.7 (IQR 6.4, 10.1) respectively. Setting and Relationship scores varied according to the age, gender, and nature of the relationship among tuberculosis cases and their contacts. Family members had a higher median setting score (13.8, IQR 11.6, 15.7) than non-family members (7.2, IQR 6.2, 9.4). The median relationship score in family members (9.9, IQR 7.6, 11.5) was also higher than in non-family members (6.9, IQR 5.6, 8.1). For both factors, household contacts had higher scores than extra-household contacts (p < .0001). Contacts of male cases had a lower setting score as opposed to contacts of female cases. In contrast, contacts of male and female cases had similar relationship scores.


In this large cross-sectional study from an urban African setting, we identified two factors that can assess adequate contact between tuberculosis cases and their social network members. These findings also confirm the complexity and heterogeneity of social mixing.

Item ID: 66557
Item Type: Article (Research - C1)
ISSN: 1471-2458
Keywords: Tuberculosis; Contact; Transmission; Social network; Contact network; Social mixing
Copyright Information: © The Author(s). 2020 Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated in a credit line to the data.
Funders: National Institute of Allergy and Infectious Disease (NIAID), Fogarty International Center, National Institutes of Health (FICNIH), Schlumberger Foudation (SF)
Projects and Grants: FICNIH R01 AI093856, FICNIH NO1-AI95383, FICNIH D43-TW0100, SF Faculty for the Future Fellowship
Date Deposited: 04 Mar 2021 02:29
FoR Codes: 42 HEALTH SCIENCES > 4206 Public health > 420606 Social determinants of health @ 100%
SEO Codes: 20 HEALTH > 2004 Public health (excl. specific population health) > 200499 Public health (excl. specific population health) not elsewhere classified @ 100%
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