Naked Science Forum

Life Sciences => Physiology & Medicine => COVID-19 => Topic started by: nudephil on 12/05/2020 17:29:32

Title: What is the probability of cross-contamination when putting a facemask on?
Post by: nudephil on 12/05/2020 17:29:32
Here's a question from listener Paul...

What is the probability of cross-contamination with SARS-CoV-2 when putting a facemask on? With hands that have handled items bought in the supermarket, and then the straps on the facemask touch the eyes and nose, thereby cross-contaminating with a potentially small viral load from grocery package to hand to facemask to eye...

Any thoughts? My instinct is, in that scenario, pretty high probability.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: alancalverd on 12/05/2020 17:55:34
Wash your hands before you gown up, and don't wear a contaminated mask.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: Bored chemist on 12/05/2020 18:17:23
Taking the mask off again is also a big contamination risk.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: alancalverd on 12/05/2020 23:31:16
A good point. The tie-on surgical mask is removed by untying and moving the ties away from the face, so although its primary purpose is to prevent exhalation rather than inhalation of pathogens, it is less likely to infect the eyes during removal than an elasticated "fitted" inhalation mask with a band that goes round the back of the head.

I've made some simple fitted masks with rubber bands that just loop over the ears and can be taken off with the same movement as a plain surgical mask.  Time to refine the design.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: set fair on 12/05/2020 23:44:28
If you don't wash or sanitize your hands after touching potentially contaminated surfaces or objects then your hands are potentially contaminated and you risk catching covid-19. If you do wash or sanitise your hands, then you won't cross contaminate. The mask is a red herring. If you think wearing a mask makes it more likely that you will cross cataminate perhaps you should consider running for President of The United States.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: alancalverd on 13/05/2020 00:00:32
The herring will be loaded with pathogens if it has done its job.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: set fair on 13/05/2020 00:24:27
The herring will be loaded with pathogens if it has done its job.


That is not an answer to the question in the OP. Wearing masks is about stopping pre/a symyptomatic people from spreading the virus.
Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: RD on 13/05/2020 02:45:21
The herring will be loaded with pathogens if it has done its job.

An orange would smell better ...

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Title: Re: What is the probability of cross-contamination when putting a facemask on?
Post by: alancalverd on 13/05/2020 09:17:46
That is not an answer to the question in the OP. Wearing masks is about stopping pre/a symyptomatic people from spreading the virus.

On the contrary, the OP is concerned with the acquisition of virus,
Quote
from grocery package to hand to facemask to eye...
not its transmission to others.

There is a lot of confusion among the public and journalists about this. Loose-fitting disposable ("surgical") masks are intended to prevent the wearer from sneezing and spitting on the patient, but don't need to filter the incoming clean air that we try to ensure in wards and theaters. Close-fitting masks as regularly worn by builders and firefighters filter the incoming air and are normally only worn in a medical setting when handling infectious patients.

The PPE crisis in hospitals and care homes cannot be resolved by surgical masks as the problem is primarily one of patients (who by definition are already infected)  infecting staff (the majority of whom are not infected), not the other way around. The requirement is to provide fitted HEPA masks to protect the staff, and the OP asks a similar question: how to protect yourself against infection acquired from handling contaminated material or removing a contaminated mask.

It's worth reviewing the effectiveness of visors. A visor certainly protects against projectile transmission but not against suspended aerosol. Goggles may be better eye protection but they need ventilation so again a HEPA  filter is required if they are to be really effective.

When dealing with a virulent airborne infection you need to forget "sterile" and think "HAZMAT".