The WHO have been giving pandemic advice for years. Here's some advice from the Jan 2020 update, just before they realised that the shit hit the fan big time and that 7.5 billion people were a few too many to provide with face masks.
With pre-symptomatic and asymptomatic spreads being a notable problem with coronavirus, we need the public to wear face coverings to stop egress (plus all the other distancing, hand washing, face washing,, clothes washing, glasses washing {can't believe nobody in this country remembers to say this} and no face touching additionally no mask touching).
If a mask fits, it is quite comfortable and does not need fiddling with. Go for ties not ear elastic, it may just be my ears but ouch - great discomfort.