What is the predicted transmission potential in locations outside of Wuhan once new cases are introduced?

Bottom Line:

Using data collected from the number of COVID-19 cases both within and outside of Wuhan between December 2019 and February 2020, it was predicted that once four or more independent cases are introduced in an area, there is a 50% chance of infection spreading in that location.


Adam J Kucharski, Early dynamics of transmission and control of COVID-19: a mathematical modelling study. The Lancet Infectious Diseases (2020). DOI:https://doi.org/10.1016/S1473-3099(20)30144-4

Date Published:

11 March 2020


Understanding transmission trends in the early stages of an infection pandemic is important in evaluating the effectiveness of control measures to prevent further disease spreading. Researchers used mathematical models on data collected both within and outside of Wuhan during December 2019 and February 2020 to predict how the introduction of travel control measures affected transmission. In the study, they calculated the daily reproduction number, which is defined as the average number of new cases each day caused by the transmission of an infected individual. It was reported that the reproduction number in Wuhan one week before travel restrictions on January 23, 2020 was 2.35; however, this number decreased to 1.05 one week following travel control measures. Furthermore, it was calculated that once there are at least four independently introduced cases outside of Wuhan, there is about a 50% chance the infection will continue to spread within that location. These results highlight the importance of implementing travel control measures in mitigating viral transmission between individuals and populations.

Summary by: Edwin Wong