A mathematical model for estimating the age-specific transmissibility of a novel coronavirus

Background: A novel coronavirus named as "SARS-CoV-2" has spread widely in many countries since December 2019, especially in China. This study aimed to quantify the age-specific transmissibility by using a mathematical model. Methods: An age-specific susceptible - exposed - symptomatic - asymptomatic - recovered - seafood market (SEIARW) model was developed based on two suspected transmission routes (from market to person and person to person). The susceptible people from Wuhan City were divided into different age groups. We used the subscript i and j to represent age group 1 to 4 (1: <= 14 years; 2: 15-44 years; 3: 45-64 years; 4: >= 65 years) and 1 to 5 (1: <= 5 years; 2: 6-14 years; 3: 15-24 years; 4: 25-59 years; 4: >= 60 years), respectively. Data of reported COVID-19 cases were collected from one published literature from 26 November to 22 December, 2019 in Wuhan City, China. The age-specific transmissibility of the virus was estimated accordingly secondary attack rate (SAR). Results: The age-specific SEIARW model fitted with the reported data well by dividing the population into four age groups (χ2 = 4.99 × 10-6, P > 0.999), and five age groups (χ2 = 4.85 × 10-6, P > 0.999). Based on the four-age-group SEIARW model, the highest transmissibility occurred from age group 2 to 3 (SAR23 = 17.56 per 10 million persons), followed by from age group 3 to 2 (SAR32 = 10.17 per 10 million persons). The lowest transmissibility occurred from age group 1 to 2 (SAR12 = 0.002 per 10 million persons). Based on the five-age-group SEIARW model, the highest transmissibility occurred from age group 4 to 5 (SAR45 = 12.40 per 10 million persons), followed by from age group 5 to 4 (SAR54 = 6.61 per 10 million persons). The lowest transmissibility occurred from age group 3 to 4 (SAR34 = 0.0002 per 10 million persons). Conclusions: SARS-CoV-2 has high transmissibility among adults and elder people but low transmissibility among children and young people.