Health Secretary Matt Hancock has said he has not been advised to change the UK’s approach to members of the public wearing face masks, as the US Government formalises guidance to recommend many Americans wear them to help fight Covid-19.

He told Good Morning Britain on Friday: “Masks are very important to protect healthcare workers… but that (asking the public to wear them) isn’t something that we’ve done here because we’ve followed the advice and we’ve followed the medical and scientific advice and the whole basis of our response has been making sure that we follow the science.”

Here is what we know about the guidance on masks as it stands:

– What is the situation in the US?

Officials in New York City are urging people to wear masks when they go outside.

Mayor Bill de Blasio said coverings for the nose and mouth can be “real homegrown” and made from a scarf or bandana.

Los Angeles mayor Eric Garcetti has also encouraged his city’s residents to cover their faces when out in public.

It is believed the new US Government guidance would suggest non-medical masks, T-shirts or bandanas be used to cover the nose and mouth when outside the home, while professional-grade masks are kept for healthcare workers.

– Are there any concerns about such a move?

Professor Susan Michie, of University College London, said there is “not good evidence” to suggest wearing masks will cut transmissions.

She said: “They do not protect against the virus getting into the eyes – only close fitting goggles do this.

“People may not fit the masks properly or take them on and off. Touching face masks and not taking them off in the correct way may mean people contaminate their hands and spread the virus.

“People may have a false sense of reassurance and thus pay less attention to other behaviours key to reducing transmission such as social distancing and hand-washing.”

– Who should wear a mask?

The World Health Organisation (WHO) has said only those with Covid-19 symptoms and those caring for them need masks, but this guidance is set to be reviewed.

Masks worn by sick people protect others from the infection through the droplets that come out when they cough or sneeze.

People caring for them should also cover up whenever they are in the same room as the patient to prevent the spread of the virus.

But the WHO says surgical masks can only help when used with other preventative measures such as frequent hand-washing.

– Are other countries ordering citizens to wear masks?

In Europe, Austria, Slovakia, the Czech Republic and Bosnia-Herzegovina have introduced these measures.

Residents in the Philippines have to wear a mask in public, and the same is true in some of the worst-affected provinces in China.

In Japan, where masks were already a household staple, the government plans to post two gauze masks to each of the country’s 50 million households.

People in Hong Kong, South Korea, Thailand and Taiwan regularly wear masks because of air pollution.