Director-General Tedros Adhanom Ghebreyesus said that the new guidance is an update of what World Health Organization has been saying for months - masks should only ever be used as part of a comprehensive strategy in the fight against COVID-19.
Dr Maria Van Kerkhove, the WHO's Covid-19 technical lead, said the organisation's updated guidance on face masks was based on "new, novel research that we didn't have a month ago".
But the advice has been broadened to recommend staff coming into contact with any patients or residents in clinics, hospitals, care homes, and long-term residential facilities should also wear masks at all times, she said.
WHO also widened its mask guidance to specify that health workers in areas where the virus is spreading freely should always wear masks inside medical facilities.
'Masks are only of benefit as part of a comprehensive approach in the fight against COVID-19.
The guidelines also recommend healthcare workers in areas of wide transmission to wear medical masks in clinical settings, even if they're not working directly with COVID-19 patients. It is recommended that fabric masks should consist of at least three layers of different materials and the full details are outlined in its guidelines.
Everyone else should use what it terms non-medical or fabric masks.
Director-General, Tedros Adhanom Ghebreyesus, listed new precautions on Friday at virtual news conference.
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'Based on this new research, World Health Organization advises that fabric masks should consist of at least three layers of different material.' said Dr Tedros said.
Tedros warned that while masks help protect people from contracting the virus, they can also be an avenue for infection if not handled properly.
Wearing face masks is an "altruistic act" and primarily a tool for "source control" in the community - in which the practice is more about protecting others if you are infected than protecting yourself, Dr. Mike Ryan, WHO executive director of health emergencies programme, said Friday.
With a fabric mask, "right now we only know that it provides a certain level of barrier, but we don't know if that's enough to prevent", Baller said.
But the United Nations health agency stressed that facemasks alone "will not protect you from Covid-19" - and people suffering with the virus should not be out in public if they can possibly avoid it.
"We have new research findings".
The WHO has stated that the cornerstone of the response in every country must be to find, isolate, test and care for every case, and to trace and quarantine every contact.
"We need to be very, very, very careful that masks are not seen as an alternative to the other public health measures that are so desperately needed".