Estimation of country-level basic reproductive ratios for novel Coronavirus (COVID-19) using synthetic contact matrices

Joe Hilton; Matt J Keeling

In Figure 1 we present the results of a null-model in which there is no age-specific susceptibility (z i 1), and plot the associated scaling factor σ for each of the 152 countries included in Prem et al.'s study. That is, we assume that the reproduction matrix R is directly proportional to the contact matrix K. The constant of proportionality will be the ratio between the leading eigenvalues of the two matrices, i.e. R 0 divided by the leading eigenvalue of K. To obtain the reproduction matrix for some other country, we just multiply its contact matrix by the constant of proportionality we estimate for China. Figure 2 presents the estimated scaling factors based on the age distribution reported by two studies of the early dynamics in China: Li et al. [1] which reports on the first 425 confirmed cases; and Yang et al. [2] which examines data from the first 4021 confirmed cases. (Our estimates of the scaling factors for each of the 152 countries is given in the Supplementary Material.)