HKU estimates 232,000 infected in Wuhan in mid-February, 2.8 times the reported total for China

There are more than a million cases of Wuhan coronavirus in Europe and the United States and yet the epidemic has not even peaked. In stark contrast, mainland China, the country where the outbreak started, has only about 82,000 cases, leading the public to question the true scale of the outbreak. The Hong Kong University School of Public Health's WHO Collaborating Centre for Epidemiology and Control of Infectious Diseases has found that had mainland China broadened its case definition criteria earlier; and screened all those with respiratory symptoms, who have been to Wuhan and surrounds, or who have been in contact with suspected cases; it is estimated that by 20 February, the number of patients with Wuhan pneumonia would have reached 232,000, about 2.8 times the current reported total cases in the mainland.

The study was co-authored by the founding director of the centre Gabriel Leung and co-director Ben Cowling, and published in The Lancet, an authoritative medical journal.

According to the research, the first diagnostic criteria adopted by the mainland as of 17 January included only those who had traveled to Wuhan or the Huanan Seafood Market, had fever and pneumonia, positive genetic sequencing and gene maps. After 3 days, the criteria were broadened to include Wuhan residents who have been exposed to infected cases or clusters with a positive RT-PCR test. The study estimates that this change alone, increased the case total by 7.1 times.

The diagnostic criteria have been changed multiple times thereafter, up to the fifth edition of the guidelines as issued on February 20, which includes individuals with either a history of travel to Wuhan and environs or epicentres of outbreak, or have contact history with suspected cases who have been to Wuhan, or a positive RT-PCR test. The study found that with every revision, the total number of cases increase by 2.6 to 3.7 times. It is estimated that by 20 February, there would have actually been 232,000 patients with meeting the diagnostic criteria for Wuhan pneumonia, of which 127,000 would be from Wuhan and 55,000 from cities in Hubei province outside Wuhan, and 50,000 people from other areas. At present, there are about 82,000 cases in the mainland, in other words, the study estimates the actual figure to be 2.8 times greater.

The study further pointed out that the mainland officially announced 1 January as the date of disease onset for 114 patients. However had the mainland adopted the fifth edition of the criteria at that point in time, 11,000 patients would have been identified with onset on 1 January, an increase of 96 times.

Does the research show that testing in mainland China was done too late and that the overall response was too slow? The paper did not provide an answer, but mentioned that for some diseases that can simultaneously cause mild and severe diseases, the number of patients found by the medical system is far less than the actual. This ‘tip of the iceberg’ phenomenon is consistent with past experience. After the mainland gradually expanded the scope of diagnosis, many suspected cases have been isolated and treated to prevent the limitless spread of the pandemic.

However, the paper also pointed out that this phenomenon is also a warning to countries with the most severe outbreaks. The number of cases will continue to increase after broader testing. The team believes that other countries should consider contingency plans, such as Switzerland’s decision to test for Wuhan coronavirus only for severe cases, or including radiological diagnostic criteria such as computed tomography (CT).

Sources: Apple Daily HK ; The Lancet, April 2020

https://bit.ly/2xVfqAP

https://www.thelancet.com/journals/lanpub/article/PIIS2468-2667(20)30089-X/fulltext