Defining adequate contact for transmission of Mycobacterium tuberculosis in an African urban environment
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Date
2020
Journal Title
Journal ISSN
Volume Title
Publisher
BMC public health
Abstract
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.
Methods: 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.
Results: 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.
Conclusions: 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.
Description
Keywords
Tuberculosis, Contact, Transmission, Social network, Contact network, Social mixing
Citation
Castellanos, M. E., Zalwango, S., Kakaire, R., Ebell, M. H., Dobbin, K. K., Sekandi, J., ... & Whalen, C. C. (2020). Defining adequate contact for transmission of Mycobacterium tuberculosis in an African urban environment. BMC public health, 20(1), 1-11. https://doi.org/10.1186/s12889-020-08998-7