BEIJING (BLOOMBERG) - The number of new coronavirus cases reported by Hubei province dropped sharply after China changed the way it officially reports the number of infections for the second time in a month, raising questions over the reliability of data from the epicentre of the outbreak.

In its daily tally, Hubei said on Thursday (Feb 20) that it had just 349 additional confirmed cases, compared with almost 1,700 additional cases from the day before.

No explanation was given for the sudden decline, but it came a day after new national guidelines advised the province to report only two numbers in its overall count: confirmed and suspected cases, in line with how other provincial and national figures are reported.

Prior to that, Hubei had been reporting whether new cases of infection were confirmed via CT scans or nucleic acid tests.

This practice was itself in place for only a week, and resulted from a methodology change made on Feb 13, which abruptly added nearly 15,000 cases to its total count.

The shifting classification guidelines, and the lack of clarity over whether cases confirmed via CT scans are still included in China's official count, forced yet another re-calculation of the contours of the crisis that has infected over 70,000 and killed over 2,000.

There is growing mistrust over official data emerging from China, which has the vast majority of coronavirus cases and deaths globally, and suspicion that the country's officials are prematurely promoting a narrative that the outbreak is coming under control.

The National Health Commission and the Hubei provincial health commission did not respond to questions seeking clarity over the latest data.

"It points to a rather concerning confusion over how best to officially report the number of cases, leading to a loss of confidence in the true numbers," said Mr Jeffrey Halley, a Singapore-based senior market analyst with Oanda Asia Pacific.

"That could mean that internationally, the rest of the world keeps China in lockdown for longer, which will not be good for the 'V-shaped recovery' projections," he said.

CT scans are an alternative method that doctors in Hubei have been using to spot signs of pneumonia in patients due to the lack of nucleic acid test kits that can identify the virus' genetic sequence in patients.

The kits themselves were also known to sometimes throw up false negatives.

In recognition of the inadequacy of testing kits, China advised Hubei province on Feb 5 to begin including patients diagnosed via CT scans as a separate category under its overall count.

The province started doing so on Feb 13 in a shock adjustment that sent its total count up by 45 per cent.

A day later, China's National Heath Commission removed 108 deaths from its total number due to "double-counting" in Hubei.

"It is not normal for case definitions to be changed so frequently," said Dr Ben Cowling, a professor of epidemiology at Hong Kong University.

"I imagine that the change in case definitions has led to a change in testing practice, that is, less use of the method of clinical diagnosis via CT scans."

UNCERTAINTY AND OPACITY

The latest changes cast doubt over whether the drop in new cases - a positive sign that the epidemic is coming under control at the epicentre - can be taken at face value.

In recent days, China's leaders have sought to project optimism over the outbreak, which has shut down large parts of its economy and plunged industries from retail to aviation into crisis.

Companies and factories across China are now being urged to restart economic activity, while Chinese Premier Li Keqiang said on Monday that the outbreak is on "a positive trend".

Troubled companies in China are starting to crumble under the strain, intensifying the pressure on China's leaders to prop up its overall economy.

The government is considering direct cash infusions or mergers to stabilise the hobbled airline industry, while the People's Bank of China said it will work on supporting domestic consumption.

The government of Hainan, the southern island province where indebted conglomerate HNA Group is based, is in talks to seize control of the group after the contagion hurt its ability to meet financial obligations, according to people familiar with the plans.

In this climate, the latest methodology change in Hubei province is raising more questions than it answers.

"I think there may be genuine attempts to report as accurately as possible and this may be just a way of refining the numbers," said Mr Vishnu Varathan, Singapore-based head of economics and strategy at Mizuho Bank.

"But the pertinent point is that in this climate of uncertainty and opacity around what is going on, constant revisions may breed mistrust, which in turn is amplified by social media."