Seasonality of COVID-19 Transmission in Tropical Countries: The Case of the Health Districts of Kati and Commune VI of Bamako in Mali
Abstract:
The existence of
seasonality in COVID-19 transmission remains a major concern in the management
of COVID-19 outbreaks. To answer this question, we conducted a retrospective
cohort study using epidemiological surveillance data from the health districts
of Kati and Commune VI of Bamako. The data was collected between January 1,
2021 and December 31, 2021. Two semi-structured questionnaires included 114
cases of COVID-19, including 43 symptomatic and 71 asymptomatic, for whom 1227
contacts were identified and followed daily for 14 days. Our results showed
that 112 of the contacts followed developed the disease, i.e. an incidence rate
of 9.1%. The sex ratio was 1.5 in favour of the female sex. The incidence rate
was higher in the dry season with 13.2% 95% CI [10.3 - 16.7] compared to 6.7%
95% CI [4.6 - 9.4] in the cool season and 5.8% 95% CI [3.4 - 9.2] in the winter
period. Also, the risk of contracting COVID-19 for exposed contacts was 2.25
times higher in the dry season compared to other seasons (RR=2.25 95% CI [1.55
- 3.28]). Incidence rates were higher for average temperatures between 28 and
34 degrees Celsius, the same is true for humidity between 19 and 37%. The dry
season has been identified as favorable for the transmission of COVID-19 in our
study area. As a result, response measures must be stepped up before and during
the dry season.
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