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.
