A five-compartment model of age-specific transmissibility of SARS-CoV-2

BackgroundThe novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, also called 2019-nCoV) causes different morbidity risks to individuals in different age groups. This study attempts to quantify the age-specific transmissibility using a mathematical model.MethodsAn epidemiological model with five compartments (susceptible-exposed-symptomatic-asymptomatic-recovered/removed [SEIAR]) was developed based on observed transmission features. Coronavirus disease 2019 (COVID-19) cases were divided into four age groups: group 1, those <= 14years old; group 2, those 15 to 44years old; group 3, those 45 to 64years old; and group 4, those >= 65years old. The model was initially based on cases (including imported cases and secondary cases) collected in Hunan Province from January 5 to February 19, 2020. Another dataset, from Jilin Province, was used to test the model.ResultsThe age-specific SEIAR model fitted the data well in each age group (P<0.001). In Hunan Province, the highest transmissibility was from age group 4 to 3 (median: (43)=7.71x10(-9); SAR(43)=3.86x10(-8)), followed by group 3 to 4 (median: beta (34)=3.07x10(-9); SAR(34)=1.53x10(-8)), group 2 to 2 (median: beta (22)=1.24x10(-9); SAR(22)=6.21x10(-9)), and group 3 to 1 (median: beta (31)=4.10x10(-10); SAR(31)=2.08x10(-9)). The lowest transmissibility was from age group 3 to 3 (median: beta (33)=1.64x10(-19); SAR(33)=8.19x10(-19)), followed by group 4 to 4 (median: beta (44)=3.66x10(-17); SAR(44)=1.83x10(-16)), group 3 to 2 (median: beta (32)=1.21x10(-16); SAR(32)=6.06x10(-16)), and group 1 to 4 (median: beta (14)=7.20x10(-14); SAR(14)=3.60x10(-13)). In Jilin Province, the highest transmissibility occurred from age group 4 to 4 (median: beta (43)=4.27x10(-8); SAR(43)=2.13x10(-7)), followed by group 3 to 4 (median: beta (34)=1.81x10(-8); SAR(34)=9.03x10(-8)).ConclusionsSARS-CoV-2 exhibits high transmissibility between middle-aged (45 to 64years old) and elderly (>= 65years old) people. Children (<= 14years old) have very low susceptibility to COVID-19. This study will improve our understanding of the transmission feature of SARS-CoV-2 in different age groups and suggest the most prevention measures should be applied to middle-aged and elderly people.