“While these control measures appear to have reduced the number of infections to very low levels, without herd immunity against COVID-19, cases could easily resurge as businesses, factory operations, and schools gradually resume and increase social mixing, particularly given the increasing risk of imported cases from overseas as COVID-19 continues to spread globally,” says Professor Joseph T Wu from the University of Hong Kong who co-led the research.
He continued: “Although control policies such as physical distancing and behavioural change are likely to be maintained for some time, proactively striking a balance between resuming economic activities and keeping the reproductive number below one is likely to be the best strategy until effective vaccines become widely available.”
How did the researchers arrive at their conclusion?
In the study, researchers analysed local Health Commission data of confirmed COVID-19 cases between mid-January and February 29, 2020, to estimate the transmissibility and severity of COVID-19 in four major cities – Beijing, Shanghai, Shenzhen, Wenzhou – and ten provinces outside Hubei with the highest number of confirmed COVID-19 cases.
The number of new daily imported and local cases were used to construct epidemic curves for each location by date of symptom onset, and reporting delays – time lags between the onset of a disease and the reporting of cases – were incorporated in the modelling to calculate weekly reproduction numbers.