Muniyandi, Malaisamy

Nagarajan, Karikalan

Palani, Bharathidasan

Sellappan, Senthil

NIRT Institutional Repository

SHORTCOMMUNICATIONTrans R Soc Trop Med Hyg 2021; 0: 1–3https://doi.org/10.1093/trstmh/trab099 Advance Access publication 0 2021Tracing the potential extra-household contacts of TB patients: findingsfrom a personal social network survey in a high TB burden setting inIndiaKarikalan Nagarajan∗, Malaisamy Muniyandi, Bharathidasan Palani, and Senthil SellappanDepartment of Health Economics, ICMR-National Institute for Research in Tuberculosis, Mayor Sathyamoorthy Road, Chetput, Chennai600031, India∗Corresponding author: Tel: +7299226582; E-mail: karikalan.n@nirt.res.inReceived 15 February 2021; revised 25 April 2021; editorial decision 14 June 2021; accepted 25 June 2021Background: Evidence on the extra-household contacts of TB patients who drive disease transmission is scarce.Methods: We conducted a cross-sectional personal social network survey among 300 newly diagnosed indexpulmonary TB patients to identify their first-degree extra-household contacts.Results: A significantly higher proportion of neighbourhood (3.5; 95%CI 1.3 to 7.5), occupational (3.2; 95% CI 1.3to 9.2) and friendship contacts (2.2; 95% CI 0.8 to 4.5) developed TB within 1 y of the index patient’s diagnosisthan their household contacts (0.7; 95% CI 0.3 to 1.3). Similarly, a higher proportion of extra-household contactshad TB at different time points before the index patient was diagnosed.Conclusion: Extra-household contacts of TB patients could be a potential source of TB or could be at increasedrisk of TB.Keywords: contact tracing, extra-household, neighbourhoods, social networks, TBIntroductionA systematic review on studies pertaining to household TB trans-mission highlighted that <20% of infections could be attributedto household exposure and that the remaining infections couldbe attributed to community transmission.1 There is a need tosystematically trace contacts occurring outside the householdsof TB patients.2 We undertook a study among newly diagnosedpulmonary TB patients to estimate the proportion of their extra-household contacts with TB compared with their household con-tacts with the disease.MethodsFrom February 2018 to June 2019, we enrolled 300 consec-utive adult pulmonary (drug-sensitive) TB patients who werenewly diagnosed at 24 designated microscopy centres inChennai, a south Indian metropolitan city, for a cross-sectionalpersonal social network survey (Supplementary Methods).Patients who resided for at least 1 y in the sample catchmentarea and who were willing to share their complete social networkand socialisation information were considered eligible for thestudy. A semistructured questionnaire was used to probe andlist the first-degree social network contacts of the index patientsas per standard.3 Network contacts were classified into house-hold and extra-household contacts, which included ‘extendedfamily and relatives’, ‘friends’, ‘neighbours’ and ‘occupational’contacts.4 A sample size of 300 was used in consideration of thesample sizes of published network studies in countries with ahigh TB burden. The following definitions were used:Index patients: The enrolled ‘newly diagnosed pulmonary TBpatients’ were defined as index TB patients.First-degree social network contacts or contacts: Individualswith whom the index TB patients had consistent social relations(lived, socialised, worked) during their prediagnostic and postdi-agnostic periods.Consistent social relation: Lived, socialised or worked togetherfor ≥3 d a week for at least 2–4 h.The diagnostic definition used for index TB patients and theircontacts with TB was taken from the National TB Elimination Pro-gram India.5 TB status of first-degree contacts was reported byindex patients and was further tracked and validated through© The Author(s) 2021. Published by Oxford University Press on behalf of Royal Society of Tropical Medicine and Hygiene.All rights reserved. For permissions, please e-mail: journals.permissions@oup.com1Downloaded from https://academic.oup.com/trstmh/advance-article/doi/10.1093/trstmh/trab099/6318894 by Inter-University Centre for Astronomy and Astrophysics user on 12 July 2021K. Nagarajan et al.Table 1. Validated TB status of the first-degree contacts of index patients at different time pointsContacts with a validated TB status*First-degree contacttypeWithin previous 5 to 1 yafter index diagnosisWithin 2 y of indexdiagnosis1 y before indexdiagnosisWithin 6 mo leadingup to index diagnosisWithin 1 y after indexdiagnosis(N) N (%)# (95% CI) N (%) (95% CI) N (%) (95% CI) N (%) (95% CI) N (%) (95% CI)ˆHousehold/family(1140)36 (3.1) (2.2 to 4.3) 27 (2.3) (1.5 to 3.4) 19 (1.6) (1.0 to 2.5) 14 (1.2) (0.6 to 2.0) 8 (0.7) (0.3 to 1.3)Relatives/extendedfamily (796)34 (4.2) (2.9 to 5.9) 20 (2.5) (1.5 to 3.8) 15 (1.8) (1.0 to 3.0) 11 (1.3) (0.6 to 2.4) 4 (0.5) (0.1 to 1.2)Friends (316) 43 (13.6) (10.1 to 17.8) 29 (9.1) (6.2 to 12.9) 24 (7.5) (4.9 to 11.)) 21 (6.6) (4.1 to 9.9) 7 (2.2) (0.8 to 4.5)Neighbours (169) 57 (33.7) (26.6 to 41.3) 45 (26.6) (20.1 to 33.9) 34 (20.1) (14.3 to 26.9) 25 (14.7) (9.8 to 21.0) 6 (3.5) (1.3 to 7.5)Occupational (123) 12 (9.7) (5.1 to 16.4) 10 (8.1) (3.9 to 14.4) 7 (5.6) (2.3 to 11.3) 5 (4.0) (1.3 to 9.2) 4 (3.2) (1.3 to 9.2)Total (2544) 182ˆ (7.1) (6.1 to 8.2) 131 (5.1) (4.3 to 6.0) 99 (3.8) (3.1 to 4.7) 76 (2.9) (2.3 to 3.7) 29 (1.1) (0.7 to 1.6)p <0.05 <0.05 <0.05 <0.05 <0.05*Validated TB status of contacts included: having concurrent TB or cured of TB or died of TB or TB cured and died or having presumptive TB andtested positive. It included both drug-sensitive and drug-resistant TB.# % is obtained by using contact numbers (N) as denominators.ˆ Binomial exact CI.a systematic process that involved (i) documentation verifica-tion, (ii) house visits and interviews with contacts or their fam-ilies, and (iii) interviews with healthcare providers. Validation ofcontact TB status was limited to a 5 y period before index diag-nosis and 12 mo after index diagnosis. Data quality standardsused for network surveys were followed.3 Validated TB statusof contacts was expressed in percentages with 95% CIs. Theχ2 test was used to assess differences in the proportion of val-idated TB status between different types of contacts. A geo-graphic positioning system was used to measure the distance (inmetres) between the residences, socialisation or working spotsof the index patients and their TB contacts and was expressedas the median and IQR. Analysis was conducted using STATVer. 16.0.Stata Corp., USA, and STROBE guidelines were followed(Supplementary Table S4).ResultsA total of 713 consecutive and newly diagnosed pulmonaryTB patients were screened, and 300 were found eligible. Theattributes and network characteristics of the 300 indices andtheir 2544 first-degree contacts are provided in SupplementaryTable S1. On average, one index had 10 first-degree contacts(Supplementary Table S1). Of the 300 index patients, 205 (68.3%)reported that 455 (17.89%) of their first-degree contacts had TBin the past or currently (Supplementary Table S2). Of the totalreported contacts with TB status (n=455), cumulative validationwas possible for 182 (40%) in the prescribed time frame of 5 ybefore to 1 y after index diagnosis. Of these 182 contacts, 131,99 and 76 statuses were validated as 2 y after, 1 y after and6 mo before the index diagnosis, respectively, and 29 statuseswere validated within 1 y after the index diagnosis. Of the 182contacts, 79.8% were first-degree validation, that is, gold stan-dard (Supplementary Table S1 and Supplementary Figure S1).Table 1 shows that, of the contacts who developed TB within1 y of the index patient’s diagnosis, a significantly high propor-tion were extra-household contacts: neighbours (3.5; 95% CI 1.3to 7.5), occupational contacts (3.2; 95% CI 1.3 to 9.2) and friends(2.2; 95% CI 0.8 to 4.5) compared with household contacts (0.7;95% CI 0.3 to 1.3; p=0.00). Of the contacts who developed TB inthe 6mo before the index diagnosis, a significantly higher propor-tion were neighbours (14.7%; 95% CI 9.8 to 21.0), friends (6.6%;95% CI: 4.1 to 9.9) and occupational contacts (4%; 95% CI 1.3 to9.2) compared with household contacts (1.2; 95% CI: 0.6 to 2.0).Similar trends highlighting a significantly high proportion of extra-household contacts with TB were observed at 1, 2 and 5 y beforeindex diagnosis. The median distance between the residences ofindex patients and their extended family contacts with TB was20 m, 60 m from neighbours, 88 m from friends and 224 m fromoccupational contacts (Supplementary Table S3).DiscussionOur results highlight that a significant proportion of extra-household contacts, especially neighbours and friends of indexpatients, had TB in the past or developed TB within 1 y ofindex patients’ diagnoses compared with the patients’ house-hold contacts. Almost half of the contacts who developed TBafter the index patients’ diagnoses were neighbours and friends.The greater chance of contracting TB among neighbours is dueto living in close proximity to the index patient’s residence.6Such a spatial perimeter could be of use for the contact tracersto prioritise contacts who are both socially and spatially closerto index patients. Thus, close geographical proximity and social2Downloaded from https://academic.oup.com/trstmh/advance-article/doi/10.1093/trstmh/trab099/6318894 by Inter-University Centre for Astronomy and Astrophysics user on 12 July 2021Transactions of the Royal Society of Tropical Medicine and Hygienerelationships could hold significant potential in driving diseasetransmission outside households.6,7 Our findings have some lim-itations. This study was conducted in a high TB prevalence set-ting andmay not be generalised to lowprevalence settings.Whilewe used robust validation steps to confirm the contact TB statusreported by index patients (SupplementaryMethods), respondentbias may still exist.Supplementary dataSupplementary data are available at Transactions online.Authors’ contributions: conceptualisation: KN and MM; methodology:KN and MM; data collection and implementation: BP and SS; analysis: KNandMM; draft preparation: KN, MM, SS and BP; review and editing: KN, MM,BP and SS.Acknowledgements: The authors would like to acknowledge the TBpatients and their social network contacts for their participation and con-tribution in this study. The authors are thankful to the National Tuber-culosis Elimination Program (NTEP) staff of Greater Chennai Corporation,Tamil Nadu, India, for their extensive support in conducting this study. Theauthors would like to thank UNOPS and STOP TB for their financial supportin conducting this study.Funding: The study was supported by the United States Agency forInternational Development (USAID) through Tuberculosis Health Actionand Learning Initiative (THALI) grant/STOP TB Partnership/United NationsOffice for Project Services (UNOPS) under the TB free Chennai initiative(UNOPS/400/401/2017/00 052). The funders had no role in study design,data collection and analysis, decision to publish or preparation of themanuscript.Competing interests: None reported. All authors have submitted theICMJE Form for Disclosure of Potential Conflicts of Interest.Ethical approval: This study was approved by the Institutional EthicsCommittee of National Institute for Research in Tuberculosis (ICMR-NIRT),Chennai (IEC no: 2017018). All respondents received written and oralexplanations of the study and signed an informed consent form beforethe interview.Data availability: The data underlying this article cannot be shared pub-licly due to the privacy and confidentiality of individuals that participatedin the study.References1 Blok L, Sahu S, Creswell J, et al. Comparative meta-analysis of tuber-culosis contact investigation interventions in eleven high burden coun-tries. PLoS ONE. 2015;10(3):e0119822.2 Classen CN, Warren R, Richardson M, et al. Impact of social interactionsin the community on the transmission of tuberculosis in a high inci-dence area. Thorax. 1999;54:136–40.3 Nagarajan K, Das B. Exploratory, cross-sectional social network study toassess the influence of social networks on the care-seeking behaviour,treatment adherence and outcomes of patients with tuberculosis inChennai, India: a study protocol. BMJ Open. 2019;9(5):e025699.4 Nagarajan K, Das B. Tuberculosis and social networks: a narrative reviewonhow social network data andmetrics help explain tuberculosis trans-mission. Curr Sci. 2019;116(7):1068–80.5 Central TB Division, Ministry of Health and Family Welfare. IndiaTB report 2019. New Delhi. Available at https://tbcindia.gov.in/WriteReadData/India%20TB%20Report%202019.pdf [accessed June8, 2020].6 Noppert GA, Yang Z, Clarke P, et al. Contextualizing tuberculosis risk intime and space: comparing time-restricted genotypic case clusters andgeospatial clusters to evaluate the relative contribution of recent trans-mission to incidence of TB using nine years of case data fromMichigan,USA. Ann Epidemiol. 2019;40:21–7.7 Kakaire R, Kiwanuka N, Zalwango S, et al. Excess risk of tuberculousinfection among extra-household contacts of tuberculosis cases in anAfrican city. Clin Infect Dis. 2020;16:ciaa1556.3Downloaded from https://academic.oup.com/trstmh/advance-article/doi/10.1093/trstmh/trab099/6318894 by Inter-University Centre for Astronomy and Astrophysics user on 12 July 2021

Tracing the potential extra-household contacts of TB patients: findings from a personal social network survey in a high TB burden setting in India

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Tracing the potential extra-household contacts of TB patients: findings from a personal social network survey in a high TB burden setting in India

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