Yet Another Medical Study on the Nasty Contamination by Respiratory Viruses on Outer Surface of Masks
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We've all seen people tug, pull, grab and smear the outside of their facemasks, including mask proponents Trump, Fauci, Newsom, etc.
In a previous post Doctor David Lang of Wisconsin says a face mask is "basically a giant Petri dish you have strapped to your face"
Following is an interesting 2019 medical study which points out the common contamination problems associated with face masks.
"Respiratory pathogens on the outer surface of the used medical masks may result in self- contamination. The risk is higher with longer duration of mask use... Respiratory pathogens may be present on used masks layers and lead to infection of the wearer... While using masks, or during long periods of time of re-using them, these pathogens may cause infection through hand or skin contamination, ingestion, or mucus membrane contact."
Following are more excerpts. The most interesting parts I highlighted in bold text. You can read the full study here.
Contamination by respiratory viruses on outer surface of medical masks used by hospital healthcare workers
Page 7 We also aimed to identify the area on the mask surface with maximum respiratory virus concentration. Laboratory based pilot study showed maximum fluorescent contamination on upper sections of the masks, which is also the likely area to be touched on removal. Of the three positive tests in hospital-based pilot study, two samples were positive from outer sections of mask, while one sample was positive from middle section. In the main study we were able to check the location of con- tamination on a quarter of mask samples. Of the 38 mask samples, one or more viruses were isolated from four (10.5%) samples – two from middle section of masks and two from right section of the masks. This presents a large area of potential contamination which place HCW at risk when removing a mask. These data may assist in developing policies on for doffing of masks after encounter with infective cases. As a general rule, HCWs should not reuse masks, should restrict use to less than 6 h and avoid touching the outer surface of mask during doffing, and practice hand hygiene after removal.
Page 6 Theoretically, there may be a risk of infection in wearer if contaminated masks are used for prolonged time. Currently there are no data around risk associated with reuse and extended used of masks and other PPE. One study showed that influenza virus may survive on mask surface and maintained infectivity for at least 8 h [25]. Our study showed very low infection among HCWs who used masks for ≤6 h. High virus positivity on masks samples worn by HCWs who examined > 25 patients, may be due to more frequent clinical contact with infective cases and transfer of more pathogens from patients to mask surface.
Page 7 Conclusion
To maintain the functionality and capacity of the health care workforce during outbreaks or pandemics of emerging infections, HCWs need to be protected. This study provides new data, which will help developing policies for safe workplace environment. The study shows that the prolonged use of medical masks (> 6 h) and frequent clinical contact in healthcare setting increase the risk to health workers through contaminated PPE. Protocols on duration of mask use should specify a maximum time of continuous use.
Page 1 Abstract
Background: Medical masks are commonly used in health care settings to protect healthcare workers (HCWs) from respiratory and other infections. Airborne respiratory pathogens may settle on the surface of used masks layers, resulting in contamination. The main aim of this study was to study the presence of viruses on the surface of medical masks.
Methods: Two pilot studies in laboratory and clinical settings were carried out to determine the areas of masks likely to contain maximum viral particles. A laboratory study using a mannequin and fluorescent spray showed maximum particles concentrated on upper right, middle and left sections of the medical masks. These findings were confirmed through a small clinical study. The main study was then conducted in high-risk wards of three selected hospitals in Beijing China. Participants (n = 148) were asked to wear medical masks for a shift (6–8 h) or as long as they could tolerate. Used samples of medical masks were tested for presence of respiratory viruses in upper sections of the medical masks, in line with the pilot studies.
Results: Overall virus positivity rate was 10.1% (15/148). Commonly isolated viruses from masks samples were adenovirus (n = 7), bocavirus (n = 2), respiratory syncytial virus (n = 2) and influenza virus (n = 2). Virus positivity was significantly higher in masks samples worn for > 6 h (14.1%, 14/99 versus 1.2%, 1/49, OR 7.9, 95% CI 1.01–61.99) and in samples used by participants who examined > 25 patients per day (16.9%, 12/71 versus 3.9%, 3/77, OR 5.02, 95% CI 1.35–18.60).
Most of the participants (83.8%, 124/148) reported at least one problem associated with mask use. Commonly reported problems were pressure on face (16.9%, 25/148), breathing difficulty (12.2%, 18/148), discomfort (9.5% 14/148), trouble communicating with the patient (7.4%, 11/148) and headache (6.1%, 9/148).
Conclusion: Respiratory pathogens on the outer surface of the used medical masks may result in self- contamination. The risk is higher with longer duration of mask use (> 6 h) and with higher rates of clinical contact.
Protocols on duration of mask use should specify a maximum time of continuous use, and should consider guidance in high contact settings. Viruses were isolated from the upper sections of around 10% samples, but other sections of masks may also be contaminated. HCWs should be aware of these risks in order to protect themselves and people around them.
Keywords: Mask, Health care workers, Viruses, Infection control
Virus positivity was significantly higher in masks samples worn for > 6 hours. Most of the participants (83.8%, 124/148) reported at least one problem associated with mask use. Commonly reported problems were pressure on face (16.9%, 25/148), breathing difficulty (12.2%, 18/148), discomfort (9.5% 14/148), trouble communicating with the patient (7.4%, 11/148) and headache (6.1%, 9/148).
Page 2 Reuse and extended use of masks are also common in many parts of the world, particularly during outbreaks and pandemics [8, 9]. Respiratory pathogens may be present on used masks layers and lead to infection of the wearer [10]. In hospital settings, these patho- gens may be generated from breathing, coughing or sneezing patients or during aerosol generating medical procedures [11]. Studies have shown that influenza virus can remain airborne for 3 h after a patient has passed through an emergency department [12]. While using masks, or during long periods of time of re-using them, these pathogens may cause infection through hand or skin contamination, ingestion, or mucus membrane contact [10]
Previous studies show that influenza and respiratory syncytial virus (RSV) may survive on outer surface of PPE [11–14]. A study showed that influenza viruses may survive on hard surfaces for 24–48 h, on cloth up to 8–12 h and on hands for up to 5 min
Page 2 If health departments do not provide clear guidance on the use of masks in these situations, HCWs may con- tinue using contaminated masks and may get infection [15]. The risk of self-contamination of HCWs is influenced by the mask itself, its shape and properties, and the virus concentration on its surface. To our knowledge, only one study examined the presence of contamination on mask and various bacteria were isolated from outer surface of medical masks [16].
The main aim of this study was to study the level of contamination on the surface of medical masks.
Page 2 The aim of this pilot study was to identify areas of maximum virus concentration on the surface of masks...In all three experiments, most particles were concentrated on upper right, middle and left sections of the masks (Figs. 1 and 2).
Currently there is very limited data on testing of masks surface for presence of pathogens. In previous studies influenza virus was detected on over 50% of the fomites tested in community settings during influenza season [17].