Figure 1Risk of spread outside Wuhan
(A) 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. (B) 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.

The University of Hong Kong researchers used mathematical modeling to come up with the new estimate.

With coronavirus panic raging, researchers are racing to determine how widespread the virus actually is. A group of them from the University of Hong Kong think they have the answer, estimating it stands at 75,800 in the city of Wuhan alone.

The researchers used mathematical modeling to estimate the size of the epidemic using officially reported coronavirus data and domestic and international travel data. The work was published in journal The Lancet

More than 75,000 infected 

The team of researchers were able to determine that in the early stages of the outbreak from 1 December to 25 January each person infected could have infected up to two to three other individuals on average.  The epidemic doubled in size every 6.4 days during that period infecting up to 75,815 people.

As of 25 January, the modeling suggests cases of coronavirus may have spread from Wuhan to other major Chinese cities including Guangzhou, Beijing, Shanghai, and Shenzhen. Combined they account for more than half the outbound international air travel from China. 

Given the new estimates of those infected and how quickly it’s spreading, a step-up of public health control measures are in order to prevent large epidemic areas in and outside of Wuhan, the researchers argued. The researchers said if further transmissibility of the virus could be reduced, the growth rate and size of the outbreaks across China will be reduced as well. 

Are more quarantines in order? 

Even a 25% reduction in transmissibility in all cities in China via expanded control efforts would have a big impact. If there’s a 50% reduction, it could change the status of coronavirus from rapidly expanding to slowly growing. More from Interesting Engineering

“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,” co-author Dr. Kathy Leung from the University of Hong Kong said in a press release announcing the results.

“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.”

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