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

Joe Hilton; Matt J Keeling

Here we have developed a simple model for age-structured transmission of 2019-nCoV with two components: an age-structured contact matrix dependent on the behaviour of the host population and an age-dependent susceptibility profile dependent on physiological response to infection. By using a previously-estimated synthetic contact matrix and age-stratified data, we were able to estimate age-dependent susceptibility profiles based on the first 425 and the first 4,021 cases in China. We then combined these estimated profiles with estimates of age-stratified contacts in 151 other countries to give us transmission matrices for these countries from which we could estimate the scale of basic reproductive ratios in each country relative to China. We demonstrated that taking age-specific susceptibility into account results in substantially different predictions of transmission intensity by country relative to a model without age-specific susceptibility; countries with older populations are at substantially higher risk than countries with younger populations.