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Official advice on whether people should wear masks in public could be changed after new evidence emerged suggesting they could protect people from coronavirus.

The World Health Organisation (WHO) has consistently said that only those who have symptoms or are caring for someone with COVID-19 should wear masks.

But a new study and evidence from Hong Kong indicates masks may have a protective benefit for the public and a panel of WHO experts is due to assess the evidence today with a view to potentially changing their guidance.

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Infections disease specialist Professor David Heymann, who is chairing the panel, warned that recommendations on masks were fraught with problems because people often wear them incorrectly or fail to dispose of them properly.

"There is right now a debate about the usefulness of masks because Hong Kong has provided some evidence that masks may be useful in protecting individuals from infection," he told a Chatham House briefing.

"It's not clear yet whether or not that's true.

"WHO, the group that I work with, is debating that with a group of experts around the world... to understand whether there is evidence which would call for a change in what WHO is recommending now for masks - which is that they really don't have a major role in protecting people from infection except in healthcare workers where they also wear eye protection and they also have a role from protecting others from coughs or sneezing.

"But as the evidence becomes available, it seems there will be a debate trying to decide whether masks play a role at some point in the outbreak.

"And believe me, if they do, there is a private sector healthy enough to begin producing those masks in quantities necessary."

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Data collected in Hong Kong around the use of masks has been shared confidentially with WHO and is expected to be published soon.

But a separate in Cambridge, US, found that coughs can project liquid droplets up to 6m away and that sneezes reach up to 8m.

Scientists involved in the research say their results indicate that wearing higher-quality masks could reduce the risks in some environments, particularly in badly ventilated rooms.

Meanwhile, Prof Heymann urged caution for people who choose to buy £39 antibody home testing kits advertised on Facebook which detect whether or not they have had COVID-19.

"That's up to the person, if you are buying for your own interest in knowing if you have an antibody then why not buy it?" he said.

"But the problem is that you don't know if this is a highly specific or sensitive test unless you have read the package insert or asked the company what is the sensitivity or specificity.

"It is a free world, anybody can buy what they want to buy and use it, but you need to think twice as to whether it is a wise investment for the purposes that you want the test for.

"If you want to just see if you have coronavirus antibody then you could check it.

"If you want to see if you have COVID antibody then you might want to do a little bit more detailed investigation as to what that test is telling you."

He added that it was not yet known whether having immunity to COVID-19 is long-lasting.

"We don't know yet in the new coronavirus that causes COVID-19 whether or not that coronavirus does cause long-lasting immunity and therefore we can't make too many assumptions," he added.

"It would be nice to say 'if I have antibody I feel a bit safer going back out into the public' but with the caveat that I don't understand how long that immunity would last.

"Certainly, a reinsertion strategy would say yes, people who have antibody to this coronavirus could at least begin to work possibly, depending on what a country risk tolerance is, they could begin to working properly back in society and then we will know."

Meanwhile, he said that the UK has "hopefully" avoided a major surge of demand on hospitals.

"Because Italy had been focusing on outbreak containment and wasn't watching what was happening in its hospitals and all of a sudden hospitals became overwhelmed with patients and they weren't able to accommodate them all," he said.

"They didn't have sufficient ventilators and they had a very high level of mortality occurring, so countries then adapted their strategies to a strategy that was more aimed at making sure there was not a surge of patients in the hospitals but rather there could be a more balanced arrival of patients in hospital.

"To do that, many countries developed a delay strategy and among that was the UK which has delayed a major surge, hopefully."