Annabelle Lemenuel-Diot*, Barry Clinch, Aeron C. Hurt, Paul Boutry, Johann Laurent, Mathias Leddin, Stefan Frings, Jean Eric Charoin
Objective: We present a country-specific, modified Susceptible, Exposed, Infectious, and Removed (SEIR) model of SARS-CoV-2 transmission aiming to provide accurate prediction of COVID-19 cases to optimize clinical trial recruitment, inform mitigation strategies, and facilitate rapid medication development.
Methods: Epidemiological data from more than 170 countries were obtained from the Johns Hopkins University COVID-19 Dashboard. Intercountry differences in initial exposure, cultural/environmental factors, and stringency of mitigation strategies were incorporated. Asymptomatic patients and “super-spreaders” were also factored into our model. Simulations were limited to a period of 2 months considering that the effects of certain parameters (e.g. seasonality of virus transmission, wearing of face masks, and deployment of vaccines) were sufficiently ambiguous to limit confidence in a longer simulation period.
Results: Using these data, our model estimated 71.5% of cases as asymptomatic. Without mitigation, a mean maximum infection rate of 1.08 cases/day (Intercountry range, 0.68–1.65) was estimated in symptomatic cases. From here, symptomatic and asymptomatic people were estimated to infect 3.39 and 7.71 other people, respectively, suggesting that asymptomatic persons could be responsible for 85% of new infections. An estimated 10.6% of cases were super-spreaders with a 2.86-fold higher transmission rate than average. Mitigation strategies with a stringency index value of ≥ 45% were estimated to be required to reduce the reproduction ratio below 1 for symptomatic cases. Simulated cases over the next 2 months differed between countries, with certain countries (eg, Argentina and Japan) likely to experience an accelerated accumulation of cases.
Conclusion: Together, results from our model can guide the distribution of diagnostic tests, impact clinical trial development, support medication development and distribution, and inform mitigation strategies to reduce COVID-19 spread. The large contribution of asymptomatic cases in the transmission also suggests that measures such as wearing masks, social distancing, testing, and vaccination deployment are foundational to slowing the spread of COVID-19.