Wearing a face mask is certainly not a sure guarantee that you won't get sick - viruses can also transmit through the eyes and tiny viral particles, known as aerosols, can penetrate masks. However, masks can be effective at capturing droplets, which is a main transmission route of corona virus, and some studies have estimated a roughly fivefold protection versus no barrier alone.

If you are to be in close contact with someone infected, a mask cuts the chance of the disease being transmitted to you. If you are showing any symptoms of corona virus, or have been diagnosed, wearing a mask can also protect others. So masks are crucial for the health and social care workers taking care of patients and are also recommended for family members who need to care for some who is ill - ideally both the patient and carer should have a mask.

In the real world, masks will probably make little difference if you are just walking around or taking a bus so there is no need to panic and bulk-buy a huge supply of masks.