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Observational study on the characteristics of COVID-19 transmission dynamics during the first wave of the epidemic in Lusaka, Zambia


Millica Phiri
Tadatsugu Imamura
Patrick Sakubita
Nelia Langa
Moses Mulenga
Marian Matipa Mulenga
George Kapapi
Michael Mwamba
Jane Nalwimba
Deborah Tembo
Kingsley Keembe
Karen Moompizho
Nkomba Kayeyi
William Ngosa
Davie Simwaba
Paul Msanzya Zulu
Fred Kapaya
Raymond Hamoonga
Mazyanga Lucy Mazaba
Nyambe Sinyange
Muzala Kapina
Chie Nagata
Nathan Kapata
Akira Ishiguro
Victor Mukonka

Abstract

Introduction: coronavirus disease 2019 (COVID-19) transmission dynamics in the communities of low- and middle-income countries, particularly sub-Saharan African countries, are still not fully understood. This study aimed to determine the characteristics of COVID-19 secondary transmission during the first wave of the epidemic (March-October 2020) in Lusaka, Zambia.


Methods: we conducted an observational study on COVID-19 secondary transmission among residents in Lusaka City, between March 18 and October 30, 2020. We compared the secondary attack rate (SAR) among different environmental settings of contacts and characteristics of primary cases (e.g, demographics, medical conditions) by logistic regression analysis.


Results: out of 1862 confirmed cases of COVID-19, 272 primary cases generated 422 secondary cases through 216 secondary transmission events. More contacts and secondary transmissions were reported in planned residential areas than in unplanned residential areas. Households were the most common environmental settings of secondary transmission, representing 76.4% (165/216) of secondary transmission events. The SAR in households was higher than the overall events. None of the environmental settings or host factors of primary cases showed a statistically significant relationship with SAR.


Conclusion: of the settings considered, households had the highest incidence of secondary transmission during the first wave in Lusaka, Zambia. The smaller proportion of contacts and secondary transmission in unplanned residential areas might have been due to underreporting of cases, given that those areas are reported to be vulnerable to infectious disease outbreaks. Continuous efforts are warranted to establish measures to suppress COVID-19 transmission in those high-risk environments.


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eISSN: 1937-8688