The true number of people infected with the deadly Wuhan coronavirus is more than 75,000, according to a scientific model, which claims the official number for those infected is far too low.
Academics at the University of Hong Kong published a paper on Friday in The Lancet, a prestigious medical journal, estimating the rate at which the virus is spreading.
It used official data on the number of infections to calculate what it said was the true extent of the disease — almost 100 times the official figures.
Underpinning the analysis is the idea that the number of international cases is disproportionately high given the number of people who travel from Wuhan to other countries.
Figure 1. Risk 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.
An aerial view shows residential and commercial buildings of Wuhan in China's central Hubei province on January 27, 2020, amid a deadly virus outbreak which began in the city.
The academics used the international figures to reverse-engineer a total for the number of cases among greater Wuhan's population of around 19 million.
Figure 2. Posterior distributions of estimated basic reproductive number and estimated outbreak size in greater Wuhan. Estimates are as of Jan 25, 2020. Cases corresponded to infections that were symptomatic or infectious. The number of cases was smaller than the number of infections because some individuals with the infection were still in the incubation period. We assumed that infected individuals were not infectious during the incubation period (ie, similar to severe acute respiratory syndrome-related coronavirus37). PDF=probability density function. FOI=force of infection.
They said that, as of January 25, they estimated that the number of cases was 75,815.
According to CNN, the official total on January 25 for the whole of Hubei province, which includes greater Wuhan, was 761, barely 1% of the total projected by the scientists.
Medics help a patient walk into a hospital in Wuhan, China, on January 26, 2020. Getty Images
The paper is not the first to suggest that the official figures do not adequately capture the scope of the outbreak. A paper from Imperial College London published on January 17 suggested that the figures were too low by a factor of 35.
As part of their model, the Hong Kong academics predicted that the scale of the virus would double every 6.4 days. By that logic, the number of people in greater Wuhan with the virus as of this Friday (January 31) would be 151,630.
Figure 3. Estimated number of cases exported to the Chinese cities to which Wuhan has the highest outbound travel volumes Estimates are as of Jan 26, 2020. Data are posterior means with 95% CrIs. FOI=force of infection.
The official number of cases on January 31 was less than 10,000. The number increased to around 12,000 as of February 1 local time.
The authors of the study said they had taken into account the effect of the dramatic lockdown imposed on Wuhan and surrounding cities last week.
Figure 4. Epidemic forecasts for Wuhan and five other Chinese cities under different scenarios of reduction in transmissibility and inter-city mobility.
However, they said that its overall effectiveness would be "negligible" given that a critical mass of cases had already been observed in several other cities.
In a meeting on Thursday, the World Health Organization declared the coronavirus outbreak a global health emergency.
An aerial view of Wuhan after a city-wide lockdown was imposed. Hector Retamal / AFP / Getty
On Friday, the US government announced a ban on any foreigner entering the country within 14 days of being in mainland China. It said US citizens would be allowed to enter but placed in quarantine.
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This article first appeared on Business Insider.
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