New Epidemiological Study Estimates About 75,800 People Infected In Wuhan And New Epicenters Sprouting Up All Over China

A novel modeling research, published in The Lancet, estimates that up to 75,800 individuals in the Chinese city of Wuhan may have been infected with 2019 novel coronavirus (2019-nCoV) as of January 25, 2020. The findings of the study could infer many implications as to the actual dire situation the world is in right down along with what possible future scenarios could be.


Major routes of outbound air and train travel originating from Wuhan during chunyun, 2019. Darker and thicker edges represent greater numbers of passengers. International outbound air travel (yellow) constituted 13·5% of all outbound air travel, and the top 40 domestic (red) outbound air routes constituted 81·3%. Islands in the South China Sea are not shown. Credit: Wu, et al. / The Lancet

Professor Dr Gabriel Leung from the University of Hong Kong who is also the senior author of the research told Thailand Medical News, “Not everyone who is infected with 2019-nCoV would require or seek medical attention. During the urgent demands of a rapidly expanding epidemic of a completely new virus, especially when system capacity is getting overwhelmed, some of those infected may be undercounted in the official register.

Furthermore there is also confirmed evidence that there are not even enough test kits in the country and that many with symptoms were turned away from hospitals.

Dr Leung added, “The apparent discrepancy between our modeled estimates of 2019-nCoV infections and the actual number of confirmed cases in Wuhan could also be due to several other factors. These include that there is a time lag between infection and symptom onset, delays in infected persons coming to medical attention, and time taken to confirm cases by laboratory testing, which could all affect overall recording and reporting.”

The research estimates also suggest that multiple major Chinese cities might have already imported dozens of cases of 2019-nCoV infection from Wuhan, in numbers sufficient to initiate local epidemic.

The first estimates underscore that it will likely take rapid and immediate scale-up of substantial public health control measures to prevent large epidemics in areas outside Wuhan. Further analyses suggest that if transmissibility of the coronavirus could be reduced, both the growth rate and size of local epidemics in all cities across China could be reduced.


Cumulative number of confirmed cases of 2019 novel coronavirus as of Jan 28, 2020, in Wuhan, in mainland China (including Wuhan), and outside mainland China. Credit: Wu, et al. / The Lancet

Lead author Professor Joseph Wu from the University of Hong Kong added, “If the transmissibility of 2019-nCoV is similar nationally and over time, it is possible that epidemics could be already growing in multiple major Chinese cities, with a time lag of one to two weeks behind the Wuhan outbreak. Large cities overseas with close transport links to China could potentially also become outbreak epicenters because of substantial spread of pre-symptomatic cases unless substantial public health interventions at both the population and personal levels are implemented immediately.”

Dr Leung further added, “Based on our estimates, we would strongly urge authorities worldwide that preparedness plans and mitigation interventions should be readied for quick deployment, including securing supplies of test reagents, drugs, personal protective equipment, hospital supplies, and above all human resources, especially in cities with close ties with Wuhan and other major Chinese cities.”

For the research, the team used mathematical modeling to estimate the size of the epidemic based on officially reported coronavirus case data and domestic and international travel (i.e., train, air, road) data. They assumed that the serial interval estimate (the time it takes for infected individuals to infect other people) for 2019-nCoV was the same as for severe acute respiratory syndrome (SARS: table 1). ( Use link at bottom of article to access the study to see the tables and figures.) The researchers also modeled potential future spread of the coronavirus in China and internationally, accounting for the potential impact of various public health interventions that were implemented in January 2020 including use of face masks and increased personal hygiene, and the quarantine measures introduced in Wuhan on January 23.

The epidemiology researchers estimate that in the early stages of the Wuhan outbreak (from December 1, 2019 to January 25, 2020) each person infected with 2019-nCoV could have infected up to 2-3 other individuals on average, and that the epidemic doubled in size every 6.4 days. During this period, up to 75,815 individuals could have been infected in Wuhan.

Furthermore estimates suggest that cases of  the coronavirus infection may have spread from Wuhan to multiple other major Chinese cities as of January 25, including Guangzhou (111 cases), Beijing (113), Shanghai (98), and Shenzhen (80; figure 3). (please use link at bottom of article to access the study to see the tables and figures.) Together these cities account for over half of all outbound international air travel from China.

Although the estimates suggest that the quarantine in Wuhan may not have the intended effect of completely halting the epidemic, further analyses suggest that if transmissibility of 2019-nCoV could be reduced by 25% in all cities nationally with expanded control efforts, both the growth rate and size of local epidemics could be substantially reduced. Moreover, a 50% reduction in transmissibility could shift the current coronavirus epidemic from one that is expanding rapidly, to one that is slowly growing (figure 4).

Co-author Dr. Kathy Leung from the University of Hong Kong added, “It might be possible to reduce local transmissibility and contain local epidemics if substantial, even draconian, measures that limit population mobility in all affected areas are immediately considered. Precisely what and how much should be done is highly contextually specific and there is no one-size-fits-all set of prescriptive interventions that would be appropriate across all settings. On top of that, strategies to drastically reduce within-population contact by canceling mass gatherings, school closures, and introducing work-from-home arrangements could contain the spread of infection so that the first imported cases, or even early local transmission, does not result in large epidemics outside Wuhan.”

The researchers point to several limitations of their study, including that the accuracy of their estimates depend on their assumption about the zoonotic source of infection in Wuhan. They also highlight that the models assume travel behavior was not affected by disease status and that all infections eventually have symptoms, so it is possible that milder cases have gone undetected which could underestimate the size of the outbreak. Lastly, they note that their epidemic forecast was based on inter-city mobility data from 2019, and might not reflect mobility patterns in 2020, particularly in light of the health threat posed by the coronavirus.

Thailand Medical News believes that this study is accurate to a certain degree as we at TMN strongly feel that the figures are even higher. But with regard to new epicenters sprouting up, media reports from China are already indicating that cities like Huanggang, Ezhou, Huangshi, Xianning etc are fast having more individuals being infected ad starting to resemble Wuhan.There are other provinces that are also fast becoming like Hubei including Chongqing, Henan and Shanghai.

Reference: “Nowcasting and forecasting the potential domestic and international spread of the 2019-nCoV outbreak originating in Wuhan, China: a modelling study” by Prof Joseph T Wu, PhD; Kathy Leung, PhD and Prof Gabriel M Leung, MD, 31 January 2020, The Lancet.
DOI: 10.1016/S0140-6736(20)30260-9