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China's Hubei province, the center of the coronavirus outbreak, reported nearly 15,000 new cases Thursday, a stark rise that dashed hopes that the epidemic was slowing down and raised new concerns about its true scale across the country.

Most of the new cases were reported in Wuhan, the capital of the province, where the virus, now named COVID-19, is believed to have originated.

Across all of China, nearly 60,000 cases of the virus have been reported, with the latest death toll at 1,367.

The latest spike came after officials in Hubei started using new technology to diagnose cases.

Hubei had previously allowed infections to be confirmed only by RNA tests, which can take days to process. RNA, or ribonucleic acid, carries genetic information allowing for identification of organisms like viruses.

But it has now begun counting cases that have been clinically diagnosed.

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The Hubei health commission did not spell out the details of the new diagnosis method, but it said clinically diagnosed cases of COVID-19 are suspected cases with "pneumonia imaging features."

Citing health officials, Reuters reported that the cases were diagnosed using computerized tomography scans, which can reveal lung infections.

As a result, 14,840 new cases were reported Thursday in Hubei, up from 2,015 new cases across mainland China on Wednesday.

The new diagnosis method will help patients get treatment as early as possible and improve the success rate, the Hubei health commission said.

However, the new testing methodology is being used only in Hubei province, Chinese officials said.

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Before the rise in cases was reported in Hubei, the World Health Organization said Wednesday that the number of cases in China had stabilized but that it was too early to say the epidemic was slowing.

"This outbreak could still go in any direction," WHO Director-General Tedros Adhanom Ghebreyesus said at a briefing Wednesday in Geneva.

"Wartime control measures" were announced Wednesday in the Zhangwan district of the city of Shiyan in Hubei province, northwest of Wuhan, the first time Chinese authorities have announced such rules since the outbreak began. Those who defy the measures will be detained, local authorities said.

The measures, which include the closing of all buildings, took effect Thursday and will last for at least 14 days.

As China struggles to get the outbreak under control, top officials in the center of the epidemic are paying the price.

China's Xinhua news agency reported Thursday that the secretary of the provincial party committee of Hubei province, Jiang Chaolian, had been removed and would be replaced by Ying Yong, the mayor of Shanghai.

Jiang's departure follows the firings of two other senior officials in Hubei.