S’pore’s ‘gold standard’ of Covid-19 detection is far more effective than rest of world: Harvard study

SINGAPORE — Almost three times more cases of the Covid-19 virus could have been found globally if the rest of the world possessed the same “gold standard” detection capability as Singapore, a study by Harvard University researchers has found.

“We consider the detection of 18 cases by Feb 4, 2020 in Singapore to be a gold standard of near-perfect detection,” said the report’s authors, adding that they had used a model to estimate the probability of detection in other countries relative to Singapore.

The world is detecting imported cases of Covid-19 at 38 per cent of Singapore’s ability to do so, said four epidemiologists from the Harvard T. H. Chan School of Public Health in the study, that has not yet been peer-reviewed.

“Singapore has historically had very strong epidemiological surveillance and contact-tracing capacity and has shown in the Covid-19 epidemic evidence of a high sensitivity of case detection,” said the researchers.

The pre-print report, which was uploaded on online medical archive medRxiv, looked at aggregated data of imported cases as of Feb 4 from the World Health Organization (WHO), taking into account 191 territories around the world.

Imported cases are those with known travel history from China.

The researchers also compared the records with air travel data from various sources, including the International Air Travel Association, and the surveillance capacity of nations based on the Global Health Security Index (GHSI) by the Economist Intelligence Unit, which last year ranked Singapore’s preparedness for major disease outbreaks below Malaysia and Thailand.

Using a model to determine how well countries have detected imported cases, the researchers picked Singapore as a benchmark based on its demonstrated ability to pick up confirmed carriers of Sars-CoV-2, the technical name of the virus which causes the disease Covid-19.

They also cited a previous study, also by a similar team of Harvard researchers, which found that among countries with substantial travel volume, Singapore had “the highest ratio of detected imported cases to daily travel volume”.

The previous study named Singapore as a statistical anomaly which had 12 more reported import cases than what had been expected, based on daily travel volume.

The same report uploaded online last Tuesday had suggested that Indonesia, which has not detected any cases of Covid-19 so far, might have missed cases. The report was called “insulting” by Indonesian Health Minister Terawan Agus Putranto earlier this week.

Harvard Professor Marc Lipsitch said in response to the criticism that the academics had meant to be “helpful” and had conducted the study to see if the total number of detected cases was representative of the actual incidence of Covid-19.

In the latest study, the researchers, including Prof Lipsitch who was involved in both studies, said their model is 95 per cent statistically reliable.

The researchers said their model in the latest study is 95 per cent statistically reliable.

High surveillance countries, such as Thailand, Australia and South Korea, came in at 40 per cent of the city-state’s ability to detect imported cases, the study concluded. Low surveillance ones, such as several African and Middle Eastern nations, achieve just 11 per cent of Singapore’s capacity.

“Put another way, this implies that the true number of cases in travellers is at least 2.8 times the number that has been detected,” the study said.

However, Singapore’s detection is “probably not 100 per cent efficient”, and the model was also able to estimate that there are around 1.8 undetected cases for every detected Covid-19 patient in the city-state.

It noted the number of Singapore cases that have no known links to China or any recent travel history. “Singapore’s detection like that in other countries has relied largely on symptoms and travel history, so the number of asymptomatic or low-severity cases missed by such a strategy is unknown,” the authors said.

What the study implies is that the true number of Covid-19 cases could be higher than previously thought, they added.

The model proves that the number of undetected cases of coronavirus is correlated to air travel connectivity and is inverse to a country’s detection capacity — and that the risks of the virus going undetected could happen anywhere around the world.

“(This could lead) to the potential risk of self-sustained transmission, which may be an early stage of a global pandemic,” the study said.