The number of coronavirus cases in China's Hubei province dramatically jumped by 15,000 overnight. Here's why.

• China's Hubei province recorded a huge spike in the number of Wuhan coronavirus cases on Thursday, announcing almost 15,000 new cases and 242 additional deaths in just 24 hours.
• It is the largest single-day increase since the outbreak began. It came as the province - where the outbreak began - changed its methods of diagnosis.
• Hubei has started using CT scans to check people for infections and confirm cases, rather than only relying on blood tests that can take days to process and which the city of Wuhan is struggling to source.
• But the figures being reported by China were already treated with suspicion, with research suggesting the actual number infected was much higher.
• Experts also say the diagnosis method will unlikely address this gap.
• Other provinces in China have also not made the same changes as Hubei, and the country has not yet updated its overall toll, meaning the exact national figures are not known.
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Hubei province, where Wuhan is located, recorded a dramatic spike of almost 15,000 new cases and 242 new deaths in just 24 hours after provincial authorities changed their method for diagnosing cases.

The Hubei Health Commission announced Thursday that it had started using a different method to test for the coronavirus - using CT scans to check bodies for infections.

This would allow hospitals to identify the patients and isolate them faster, Reuters reported the commission as saying.

Authorities had previously used RNA tests, which require taking patients' blood and testing for the coronavirus in labs.

But getting results from this method can take days, and health authorities in Hubei have reported a shortage of test kits.

They have also been overwhelmed by the number of cases and potential cases across its cities, including Wuhan.

However, testing new cases with CT scans - rather than with blood tests - could be a less thorough method of confirming new cases. Testing with the old method require lab-test confirmation, while the new method does not.

The number of new cases on Thursday - 14,840 - is the highest reported in a single day since the outbreak began. Two hundred and twenty-four new deaths is also the biggest daily rise in the death count.

Only around 30,000 cases had been recorded in the province as of Wednesday, meaning the number of cases surged by around a third in 24 hours.

(For the latest case total and death toll, see Business Insider's live updates.)

Had officials only used the old method of blood testing in Thursday's account, they would record 1,508 new cases, Reuters reported.

Authorities said that 13,332 of the new cases were "clinically diagnosed" - meaning the new method - which rendered the 1,508 figure.

The spike in the number of new cases came as the rate of new infections appeared to be slowing. On Wednesday, China recorded its lowest number of new cases in two weeks.

But debate has raged over the accuracy of China's figures since it first started reporting on the novel coronavirus.

Suspicion surrounding the country's figures includes:

• Research suggesting that a host of symptoms are overlooked, and that there are actually eight times more cases than reported.
• A scientific model suggesting the number of infections was actually ten times higher than what was recorded near the end of January, around one month into the outbreak.
• Other research suggesting China does not have the capacity to properly test enough people in Wuhan for the virus, and that there are actually 19 times more people infected than what is recorded.
• Allegations of a cover up by Chinese authorities, who targeted medical professionals and journalists who warned about the virus in its early days.
• Suspicion around another Chinese province cutting its number of confirmed cases, after deciding that people who tested positive for the coronavirus but did not show symptoms did not count.

Other provinces in China have also not made the same changes in diagnosis methods as Hubei, and the national health authority - unusually - did not put out an updated total for the country on Thursday.

Kerry Brown, director of the Lau China Institute at King's College, London, told The New York Times on Wednesday: "It's pretty clear that there is an issue with trust about whatever the Chinese government comes out with at the moment."

"That may be terribly unfair," he told the Times. But "to redefine things - even legitimately - at a moment like this is always going to be a presentational challenge, because people are going to be very sensitive, and they're going to suspect there's another agenda," he said.

On Wednesday, the World Health Organization also warned against drawing conclusions from figures, even if they are correct.

Tedros Adhanom Ghebreyesus, the group's head, said that any apparent slow in the spread of the coronavirus should be viewed with "extreme caution," adding: "This outbreak could still go in any direction."

The ruling Communist Party has also removed and demoted a number of officials, from high-ranking politicians to lower-level health officers, and accused many of failing to adequately contain the spread of the outbreak.

With these new figures from Hubei, the coronavirus has killed more than 1,350 people and infected over 60,000 people worldwide. While the vast majority of cases are in China, the coronavirus has also spread to at least 25 other countries.

• Read more about the coronavirus:
• Here's everything we know about the outbreak
• China boasted that it built 2 new coronavirus hospitals in 12 days. But they're treating less than half the people they're supposed to.
• The US has confirmed 14 coronavirus cases across 6 states. Here's what we know about all the US patients.
• London just confirmed its first coronavirus case. One map shows where the outbreak has spread around the world.
• Here's what life in isolated, quarantined Wuhan.