The transmissibility of infection and illness is a critical component of epidemic projections and health service planning. Transmissibility is usually described by the calculation of the reproductive number R₀, representing the average number of new infections generated by an infectious person in a totally naïve population. The complete calculation of this is hampered by our non-understanding of the portion of infections which remain asymptomatic. However, based on the incidence of transmission from identified symptomatic cases to contacts, R₀ for SARS-CoV-2 ranges from 1.4 to 3²². This is higher than the estimated R₀ for 1918 pandemic influenza²³. Thus, this epidemic, which appears to be highly transmissible, is likely to have a very significant impact on the health of populations worldwide.