ESTIMATING ASYMPTOMATIC AND SYMPTOMATIC TRANSMISSION OF NOVEL
CORONAVIRUS DISEASE 2019 IN SELENGE PROVINCE, MONGOLIA
Abstract
Background: Following a locally transmitted case in Sukhbaatar city,
Selenge province, we conducted a study with two objectives. First, we
aimed to estimate the basic reproduction number of COVID-19, leveraging
the epidemiological and clinical characteristics observed in the first
67 confirmed cases. Second, we aimed to model the outbreak considering
different patient profiles - asymptomatic, symptomatic, and
pre-symptomatic - with the goal of predicting the ultimate scale of the
epidemic in the scenario of uninterrupted transmission. Methods: We
conducted a prospective case study following the WHO FFX cases generic
protocol. The rapid response teams collected the surveillance data from
November 14–29, 2020. We created a stochastic process to draw many
transmission chains from this greater distribution to better understand
and make inferences regarding the outbreak under investigation. Results:
The majority of the cases involved household transmissions (35, 52.2%),
work transmissions (20, 29.9%), index (5, 7.5%), same apartment
transmissions (2, 3.0%), school transmissions (2, 3.0%), and meetup
transmissions (1, 1.5%). The posterior means of the basic reproduction
number of both the asymptomatic cases, R_0^Asy and pre-symptomatic
cases R_0^Pre (1·35 [95% CrI 0·88−1·86] and 1·29 [95% CrI
0·67−2·10], respectively), were lower than that of the symptomatic
cases. Conclusion: Our study highlights the heterogeneity of COVID-19
transmission across different symptom statuses and underscores the
importance of early identification and isolation of symptomatic cases in
disease control. Detailed contact tracing data with advanced statistical
methods, can be applied to other infectious diseases, facilitating a
more nuanced understanding of disease transmission dynamics.