Two-Thirds of Exported nCOVID-19 WARS Cases Undetected

imperial.ac.uk |  Dr Sangeeta Bhatia, report author, explained: “We compared the average monthly number of passengers travelling from Wuhan to major international destinations with the number of COVID-19 cases that have been detected overseas. Based on these data, we then estimate the number of cases that are undetected globally and find that approximately two thirds of the cases might be undetected at this point. Our findings confirm similar analyses carried out by other groups.”

As of 20 February 2020, over 74,000 cases of COVID-19 (formerly 2019-nCoV) have been reported in China (with 2121 deaths). Over 1000 cases have been confirmed in 29 regions and countries outside mainland China (including Hong Kong SAR and Macau SAR).

Dr Natsuko Imai, report author, said: “We are starting to see more cases reported from countries and regions outside mainland China with no known travel history or link to Wuhan City. Our analysis, which extends and confirms previously released analysis by other groups using flight volumes from Wuhan City and the reported number of COVID-19 cases, demonstrates the importance of surveillance and case detection if countries are to successfully contain the epidemic."

Exported cases vary in the severity of their clinical symptoms, making some cases more difficult to detect than others. Some countries have detected significantly fewer than would have been expected based on the volume of flight passengers arriving from Wuhan City, China.

Gina Cuomo-Dannenburg, report author, added: “We compiled data from a variety of publicly available sources, such as national and provincial ministries of health and local news, to determine information about travel history, exposure and symptom onset of individual patients observed outside of mainland China. We would like to thank countries for their continued transparency in presenting information on new cases, and would like to encourage communication of patient outcomes going forward to present a true picture of severity and clinical presentation.”

Based on comparisons with Singapore only, 63% of cases are estimated to be undetected. Comparing with Singapore, Finland, Nepal, Belgium, Sweden, India, Sri Lanka, and Canada, 73% of cases are estimated to be undetected.