Scientists in Hong Kong say they have made a potential breakthrough discovery in the fight against infectious diseases – a chemical that could slow the spread of deadly viral illnesses.

In a study published this month in the journal Nature Communications, a team from the University of Hong Kong (HKU) described the newly discovered chemical as “highly potent in interrupting the life cycle of diverse viruses”.

The scientists told AFP news agency on Monday that it could one day be used as a broad-spectrum antiviral for a host of infectious diseases – and even for viruses that have yet to emerge – if it passes clinical trials.

The spread in recent decades of sometimes deadly bird flu strains, the Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) have underscored the need for new drugs that can work more quickly than vaccines.

Broad-spectrum antivirals are seen as the holy grail because they can be used against multiple pathogens.

In contrast, vaccines usually only protect against one strain, and by the time they are produced the virus may have mutated.

The HKU team tested their chemical “AM580” on mice in a two-year study and found it stopped the replication of a host of flu strains – including H1N1, H5N1 and H7N9 – as well as the viruses that cause SARS and MERS.

It also stopped the replication of the mosquito-borne Zika virus and Enterovirus 71 which causes hand, foot and mouth disease.

“This is what we call a broad-spectrum antiviral drug, which means it can kill a number of viruses,” microbiologist Yuen Kwok-yung, who led the team, told AFP.

“This is quite important in the early control of an epidemic.”

Starving the virus

The study is part of a growing body of research by virologists to find drugs that avoid targeting a virus directly – something which could lead to resistance. Instead they look for compounds that interrupt the way viruses use crucial fatty acids, known as lipids, within a host’s cells to replicate.

“This study is science in progress – an early step in an exciting new direction,” said Benjamin Neuman, an expert on viruses at Texas A&M University-Texarkana who has published his own studies on starving viruses of lipids.

“Viruses are totally dependent on supplies stolen from their hosts, and a number of recent studies have shown that treatments that interrupt the steady flow of lipids in an infected cell are highly effective at blocking a wide range of viruses,” he told AFP.

The next step is to test the drug on a wider variety of animals, including pigs and primates, before pushing to clinical trials, a process Yuen said could take up to eight years.

The HKU team have applied for a patent in the United States.

A derivative of AM580 is already being used in Japan to treat cancer, raising hopes that it will show low toxicity for humans.

But Neuman warns there are drawbacks.

Like many chemotherapy methods used to fight cancer, antivirals such as AM580 damage a person’s cells to starve a virus. While cells can heal, much research still needs to be done on how and when to use such techniques.

“Unless the treatment is targeted very carefully, the potential for side effects would be very worrying,” he said.

Densely populated Hong Kong has first-hand experience of deadly viral outbreaks.

In 2003, nearly 300 people died from SARS and the city’s densely packed apartment blocks are considered hugely vulnerable to future outbreaks.

Canada has warned its citizens of the risk of “arbitrary enforcement” of local laws in China after a Canadian man convicted of drug trafficking was suddenly retried and sentenced to death, and Beijing denied another detained Canadian diplomatic immunity.

The Canadian government on Monday updated its travel advisory for China, telling citizens to exercise a high degree of caution while in the country.

The update noted the “risk of arbitrary enforcement of local laws” and highlighted the severe penalties for drug offences, including death.

It came hours after a court inin China’s Liaoning province sentenced Robert Lloyd Schellenberg to be executed for drug smuggling following a day-long retrial in which the 36-year-old Canadian had declared his innocence.

“The court completely rejects the accused person’s explanation and defence because it is completely at odds with the facts,” the chief judge said in a courtroom packed with observers, including Canadian embassy officials.

Schellenberg had the right to appeal to Liaoning High Court within 10 days upon receiving the ruling, according to a statement by the Dalian Intermediate People’s Court.

Justin Trudeau, the prime minister of Canada, said in Ottawa that he was concerned that China had chosen to “arbitrarily” apply the death penalty to a Canadian citizen.

The Canadian government has said it is following the case “very closely” and has provided Schellenberg with consular assistance.

Schellenberg was detained in 2014 and sentenced to 15 years in prison two years later. But last month, an appeal by prosecutors claiming the sentence was too lenient was suddenly given the go-ahead. Monday’s retrial was scheduled with just four days’ notice.

Analysts and rights groups said retrials were rare in China, especially ones calling for a harsher sentence.

“China is going to face lots of questions about why this particular person, of this particular nationality, had to be retried at this particular time,” Sophie Richardson, the Washington-based China director for Human Rights Watch, told Reuters news agency.

Prosecutors said Schellenberg was the principal suspect in a case involving an international syndicate that planned to send some 222kg of methamphetamine to Australia, hidden in plastic pellets which were concealed in rubber tyres.

Two Chinese men have also been tried. One was given a life sentence and the other a suspended death sentence. 

But Schellenberg’s lawyer, Zhang Dongshuo, said prosecutors had not produced any new evidence to justify a heavier sentence. He said he planned to lodge an appeal.

China has executed other foreigners for drug-related crimes in the past, including a Japanese national in 2014 and a Filipina in 2013. Beijing considers the number of people executed in China each year to be a state secret. International human rights organisations estimate the figure at around 2,000.

The Intermediate People’s Court of Dalian, where Canadian Robert Lloyd Schellenberg was suddenly retried on drugs charges and sentenced to death [Reuters]

The death sentence adds to the tension between the two countries following the arrest in Canada last month of a top executive from telecommunications giant Huawei, infuriating Beijing.

Canada detained Meng Wanzhou, the company’s chief financial officer, on a US extradition request related to alleged Iran sanctions violations. Meng, which denies wrongdoing, has been released on bail and extradition proceedings are due to start next month.

Chinese authorities later detained two Canadian nationals – a former diplomat and a business consultant – on suspicion of endangering national security, in what has been seen by analysts as retaliation for Meng’s arrest.

‘Difficult not to see a link’

Further escalating the diplomatic rift between Ottawa and Beijing, a Chinese spokesperson said earlier on Monday that Michael Kovrig, a former Canadian diplomat taken into custody the day after Meng’s arrest, was not eligible for diplomatic immunity as Trudeau has maintained.

A senior Canadian government official said Chinese officials have been questioning Kovrig about his diplomatic work in China, which is a major reason why Trudeau is asserting diplomatic immunity.

The official, who was not authorised to comment publicly about the case, spoke on the condition of anonymity.

Kovrig, a Northeast Asia analyst for the International Crisis Group, was on leave of absence from the Canadian government at the time of his arrest last month.

Hua Chunying, a spokesperson for the Chinese foreign ministry, told reporters that Kovrig is no longer a diplomat and entered China on an ordinary passport and business visa.

“According to the Vienna Convention of Diplomatic Relations and international law, he is not entitled to diplomatic immunity,” Hua said at a daily briefing. “I suggest that the relevant Canadian person carefully study the Vienna Convention … before commenting on the cases, or they would only expose themselves to ridicule with such specious remarks.”

A former Canadian ambassador to China, Guy Saint-Jacques, said interrogating Kovrig about his time as a diplomat in China would violate Vienna Convention protections of residual diplomatic immunity that mean a country is not allowed to question someone on the work they did when they were a diplomat.

“It’s difficult not to see a link” between the case and Canada’s arrest of Meng, Saint-Jacques told The Associated Press news agency.

Hua insisted the allegation that China arbitrarily detained Canadian citizens is “totally groundless”.

Canada has embarked on a campaign with allies to win the release of Kovrig and Spavor. The United States, Britain, European Union and Australia have issued statements in support.

Trudeau called US President Donald Trump about the detentions last week and the White House called the arrests “unlawful”.