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Melbourne, Apr 10: Scientists have identified six drug candidates from more than 10,000 compounds that may help treat COVID-19.

The research, published in the journal Nature, tested the efficacy of approved drugs, drug candidates in clinical trials and other compounds.

"Currently there are no targeted therapeutics or effective treatment options for COVID-19," said Professor Luke Guddat from the University of Queensland in Australia.

"In order to rapidly discover lead compounds for clinical use, we initiated a programme of high-throughput drug screening, both in laboratories and also using the latest computer software to predict how different drugs bind to the virus," Guddat said.

The project targeted the main COVID-19 virus enzyme, known as the main protease or Mpro, which plays a pivotal role in mediating viral replication, the researchers said.

This makes it an attractive drug target for this virus, and as people don't naturally have this enzyme, compounds that target it are likely to have low toxicity, they said.

"We add the drugs directly to the enzyme or to cell cultures growing the virus and assess how much of each compound is required to stop the enzyme from working or to kill the virus. If the amount is small, then we have a promising compound for further studies," said Guddat.

After assaying thousands of drugs, researchers found of the six that appear to be effective in inhibiting the enzyme, one is of particular interest.

"We're particularly looking at several leads that have been subjected to clinical trials including for the prevention and treatment of various disorders such as cardiovascular diseases, arthritis, stroke, atherosclerosis and cancer," Guddat said.

Researchers said compounds that are already along the pipeline to drug discovery are preferred, as they can be further tested as antivirals at an accelerated rate compared to new drug leads that would have to go through this process from scratch.

"With continued and up-scaled efforts we are optimistic that new candidates can enter the COVID-19 drug discovery pipeline in the near future," Guddat said.

Beijing, Jun 17: Beijing's airports cancelled more than 1,200 flights and schools in the Chinese capital were closed again on Wednesday as authorities rushed to contain a new coronavirus outbreak linked to a wholesale food market.

The city reported 31 new cases on Wednesday while officials urged residents not to leave Beijing, with fears growing about a second wave of infections in China, which had largely brought its outbreak under control.

Tens of thousands of people linked to the new Beijing virus cluster -- believed to have started in the sprawling Xinfadi wholesale food market -- are being tested, with almost 30 residential compounds in the city now under lockdown.

At least 1,255 scheduled flights were cancelled Wednesday morning, state-run People's Daily reported, nearly 70 percent of all trips to and from Beijing's main airports.

The outbreak had already forced authorities to announce a travel ban for residents of "medium- or high-risk" areas of the city, while requiring other residents to take nucleic acid tests in order to leave Beijing.

Meanwhile, several provinces were quarantining travellers from Beijing, where all schools -- which had mostly reopened -- have been ordered to close again and return to online classes.

"The epidemic situation in the capital is extremely severe," Beijing city spokesman Xu Hejian warned Tuesday.

Mass testing under way

Officials have closed 11 markets and disinfected thousands of food and beverage businesses in Beijing after the outbreak was detected.

The city has now reported 137 infections over the last six days, with six new asymptomatic cases and three suspected cases on Wednesday, according to the municipal health commission.

An additional two domestic cases, one in neighbouring Hebei province and another in Zhejiang, were reported by national authorities on Wednesday, while there were 11 imported cases.

Authorities have so far banned group sports, ordered people to wear masks in crowded enclosed spaces, and suspended inter-provincial group tours in response to the outbreak.

Officials said that since May 30, more than 200,000 people had visited Xinfadi market, which supplies more than 70 percent of Beijing's fruit and vegetables.

More than 8,000 workers there were tested and quarantined.

Until the new outbreak, most of China's recent cases were nationals returning from abroad as COVID-19 spread globally, and the government had all but declared victory against the disease.

China's Center for Disease Control and Prevention said Monday that the virus type found in the Beijing outbreak was a "major epidemic strain" in Europe.

Wuhan, Jun 9: China on Tuesday dismissed as "incredibly ridiculous" a Harvard study, which pointed to a surge in traffic outside Wuhan hospitals from August 2019 suggesting that the coronavirus hit the area far earlier than reported.

A whitepaper on coronavirus released by China on Sunday said the virus was first noticed on December 17 and Chinese virologists confirmed human-to-human transmission on January 19, prompting authorities to impose lockdown of Wuhan from January 23.

US President Donald Trump and leaders of several countries have accused China of not being transparent in reporting the deadly disease, leading to huge human casualties and economic crisis across the world.

The new study by Harvard researchers says satellite images show an increase in traffic outside five hospitals in Wuhan from late August to December.

The traffic spike coincided with a rise in online searches for information on symptoms like "cough" and "diarrhoea".

China said the study was "ridiculous" and based on "superficial" information, BBC reported.

It is believed that the virus first appeared in China some time in November. Authorities reported a cluster of pneumonia cases with an unknown cause to the World Health Organization (WHO) on December 31.

"Clearly, there was some level of social disruption taking place well before what was previously identified as the start of the novel coronavirus pandemic," Dr John Brownstein, who led the research, told ABC news.

The study has not been peer-reviewed.

The researchers examined commercial satellite data from outside five Wuhan hospitals, comparing data from late summer and autumn 2018 to the same time period in 2019.

In one case, researchers counted 171 cars parked at one of Wuhan''s largest hospitals, Tianyou Hospital, in October 2018.

Satellite data from the same time in 2019 showed 285 vehicles in the same place, an increase of 67 per cent.

A surge in online searches for words associated with the symptoms of coronavirus on the Chinese search engine Baidu seemed to emerge at the same time.

"This is all about a growing body of information pointing to something taking place in Wuhan at the time," Dr Brownstein said.

"Many studies are still needed to fully uncover what took place and for people to really learn about how these disease outbreaks unfold and emerge in populations. So this is just another point of evidence," he said.

Asked for her reaction at the media briefing, Chinese Foreign Ministry spokeswoman Hua Chunying dismissed the findings as "incredibly ridiculous".

"I think it is ridiculous, incredibly ridiculous, to come up with this conclusion based on superficial observations such as traffic volume," she said.

"(I have) Not seen the research you mentioned. If the conclusion is drawn based on traffic volumes (and) other superficial observations, it won’t be a sound conclusion," she said and referred to the allegations about the COVID-19 originating from the Wuhan Institute of Virology (WIV) by Trump.

"That allegation was proved to be wrong," she said.

When pointed out that China says it respects science based inquiry and Harvard is one of the top universities in the world, Hua said, "on the origin of virus there are lot of conspiracy theories against China”.

"That is very unfair. At the moment, the pressing task is to enhance coordination to contain the spread of the virus. Someday, I am sure the truth will be out. China deserves a fair and objective evaluation," she said and referred to the whitepaper released by the Chinese government detailing evolution of coronavirus in Wuhan and how Beijing handled the situation.

Recently, the World Health Assembly (WHA), the decision-making body of Geneva-based World Health Organization (WHO), passed a resolution to probe the origin of the virus. China also backed the resolution.

As of Monday, the overall confirmed cases on the mainland had reached 83,043, including 58 patients who were still being treated, with no one in severe condition, China’s National Health Commission, (NHC) said.

Altogether 78,351 people had been discharged after recovery and 4,634 people had died of the disease, it said.