Just at the moment there are several types of face Masks being used and it is worth thinking a little about how they are used and why.

We know that there are very many carriers of the virus who are asymptomatic and the main reason for wearing a mask in public is to stop the spread of the virus. We also know that there may be as many as 10 times the number of people infected than those actually diagnosed (current practice is to only test those with symptoms). Therefore it is important for everyone, regardless of whether they think they are contagious or not, to wear a mask in public in order to stop the exponential spread of the virus. The surgical type mask will do little to stop you getting the virus but will stop most droplets from your breath entering the environment. Conversely the top of the line masks with valves in them will protect you from contagion, if used properly in conjunction with a face shield, but the valve is to allow the wearer's breath to easily exit and could therefore carry the virus from an infected person into the environment. This type of face mask should be used by persons who are not contagious and are exposed to people who are known or suspected to be contagious, in other words medical staff.

We know that the principal method of transmission of COVID-19 is via droplets of moisture in breath, speech, coughs and sneezes. The droplets of moisture in normal breath are very small and completely evaporate in a very short distance, without moisture and organic matter the virus can not survive very long. The larger droplets that are expelled in normal speech, coughs and sneezes may be expelled some distance from the body and fall on the floor or other objects where there may be a a small quantity of organic matter and therefore any virus may survive for an extended period.

So the logic of wearing a mask is to limit the spread of the virus from those already infected to those not yet infected and, in particular, those who may carry the virus into households with at-risk persons. To effectively do this you must wear a mask that does not allow your breath to enter the environment, in other words not the type of mask that has a valve to allow the breath to exit unfiltered.

A face mask should obviously be fitted with clean hands and, if it has a metal strip, that should be modelled to fit closely on the bridge of the nose. From that point on the mask should not be touched for any reason at all or you risk carrying contamination that you have picked up on your hands or gloves to the mask. It should always be kept above the nose and should not be removed for speech, to answer the phone etc. When it needs to be adjusted or removed touch only the elastic straps and not the mask itself and preferably after cleaning the hands. Normally these masks are used only for short periods, at the most a few hours, however with the shortage of supply most people are using the masks multiple times. UV light can be used to decontaminate the masks and several hours of sunlight can also be quite effective. Some masks that are not badly effected by moisture can be either washed or disinfected by a good steaming using a household steam iron. Remember any mask, even one improvised in cotton, is better than nothing if worn correctly. Do not use hand cleaners or gels to clean the mask: there have been several cases of intoxication of people who have used chemical cleaning materials on masks.

All this also highlights the reason behind the recommendations on what to do in the case of a cough or a sneeze. A cough or a sneeze should always be covered to limit the spread of viruses into the environment. If a disposable handkerchief is not available use the inside of the elbow to save transmitting the virus to hands which can then touch and contaminate other objects. Disposable handkerchiefs should be thrown away immediately and cloth handkerchiefs changed and washed as often as possible. Obviously hand washing or cleaning is of the highest importance as is not touching the face.

All the above is a summary of advice given by an epidemiologist, in other words not something dreamed up by an unqualified person such as myself.

Peter

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