SINGAPORE - Singapore's approach to the coronavirus outbreak is the "gold standard" for case detection, according to a new study at Harvard University, with researchers using Singapore as a benchmark for other countries.

The study concluded that the global number of cases of Covid-19, as the disease has been called, would be 2.8 times more than it is currently if every other country had the same detection capacity as Singapore.

"We consider the detection of 18 cases by Feb 4, 2020 in Singapore to be a gold standard of near-perfect detection," wrote four epidemiologists at Harvard's T. H. Chan School of Public Health.

The researchers include epidemiology professor Marc Lipsitch, postdoctoral research fellows Aimee Taylor and Pablo Martinez de Salazar Munoz, and research associate Rene Niehus.

"We estimated that detection of exported cases from Wuhan worldwide is 38 per cent as sensitive as it has been in Singapore," they wrote.

Among what the study calls "high surveillance" countries, the number was 40 per cent. The study said detection ability among "low surveillance" countries, was just 11 per cent of Singapore's.

High surveillance countries were defined as those that scored the highest on the Global Health Security Index (GHSI), which ranks countries on their disease prevention, detection, reporting and response capabilities, among other things.

The researchers also referred to a previous study from the school which highlighted Singapore as a statistical anomaly when it tried to estimate how many cases each country should have based on travel volume from China.

The researchers had examined aggregated data from a Feb 4 World Health Organisation report on the number of cases imported by travellers with known travel history to China to 191 countries and regions. The study excluded Hong Kong, Macau and Taiwan.

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The researchers then used historical data from the International Air Travel Association and other sources to estimate the number of daily air travel passengers from Wuhan, where the virus originated, to locations outside of China.

"Among countries with substantial travel volume, Singapore showed the highest ratio of detected imported cases to daily travel volume, a ratio of one case per five daily travellers," the study's authors wrote.

"Singapore is historically known for exceptionally sensitive detection of cases, for example in Sars (severe acute respiratory syndrome), and has had extremely detailed case reporting during the Covid-19 outbreak."

One implication of the latest study is that the virus could have remained undetected after being exported from Wuhan to various locations worldwide before the city was locked down on Jan 23, the authors noted.

The Harvard study was uploaded to a free online health sciences archive called medRxiv on Friday as an unpublished manuscript.

The report is complete but the website notes that such manuscripts, or preprints, are "preliminary reports of work that have not been peer reviewed" that should not be relied on to guide clinical practice or health-related behaviour.