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

María Eugenia Castellanos,Sarah Zalwango,Juliet Sekandi,Mark H Ebell,Christopher C Whalen,Kevin K Dobbin,Noah Kiwanuka,Robert Kakaire

doi:10.1186/s12889-020-08998-7

María Eugenia Castellanos, Sarah Zalwango + Show 6 more

Open Access

https://doi.org/10.1186/s12889-020-08998-7

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Abstract

BackgroundThe 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.MethodsThis 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.ResultsTuberculosis 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.ConclusionsIn 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.

Highlights

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
For any infectious disease, the transmission of the microorganism is the result of exposure, that is adequate contact between an infectious case and a susceptible host
We propose that community-based interventions that reduce the frequency and duration of adequate contact between tuberculosis cases and their contacts would be an effective way to control tuberculosis, but it is challenging to design these interventions without a better understanding of the factors that affect the dynamics of social mixing in a population

Summary

Introduction

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. The global incidence of tuberculosis has declined in the last decade, the disease persists in many low- and middle-income countries around the world [6]. These countries rely on passive case finding followed by directly-observed therapy as the mainstay of tuberculosis control, yet the disease persists. We propose that community-based interventions that reduce the frequency and duration of adequate contact between tuberculosis cases and their contacts would be an effective way to control tuberculosis, but it is challenging to design these interventions without a better understanding of the factors that affect the dynamics of social mixing in a population

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