A projectile model for pandemics : Application to early transmission and control of COVID-19 in countries and the China example

We introduce a projectile model for pandemics which shows that a pandemic without control spreads in log-time scale within a population in the form of a mechanical projectile in a free atmosphere. Hence, a controlled pandemic behaves like a “decayed” projectile motion in a resistive atmosphere. If β is the “decay polynomial” associated with the decay in amplitude and range of a projectile in a resistive atmosphere, then U by analogy will be the “control polynomial” associated with the reduction in intensity and duration of a pandemic due to control measures. By comparing the r-square of the best-fit polynomial to β (i.e Rβ 2) to the r-square of the same-degree best-fit polynomial to U (i.e Rμ 2), the parameter; ϵ = Rβ 2/Rμ 2 serves the purpose of assessing pandemic control levels for different populations. The above framework was used to assess early transmission and control of COVID-19 in 20 high-burden countries from World Health Organization (WHO) COVID-19 case trends within the first half of year 2020. Four clusters were segregated using the ϵ parameter. China and countries from Europe and North America, appeared in Cluster 1- with the most effective early COVID-19 control, while countries with less effective control mainly from Africa (although with the least transmission), Asia and South America appeared in Clusters 2, 3 and 4. The framework achieves the purpose of obtaining an objective metric for pandemic control assessment; hence China with ϵ = 1.1 showed a near projectile-type controlled transmission so that the measures adopted by China may serve as model for future pandemic control especially in Africa where poor medical and social infrastructure was evident in the poor handling of the pandemic.