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Rapid response to:


Face masks for the public during the covid-19 crisis

BMJ 2020; 369 doi: (Published 09 April 2020) Cite this as: BMJ 2020;369:m1435

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More research is needed on their effect on the nasopharyngeal and oropharyngeal bacterial flora

Dear Editor

I have performed several thousand post mortem examinations on people of all ages who have died following viral respiratory tract infections. It is most unusual for the virus to act alone. In most cases there is a secondary contribution to inflammation from nasopharyngeal and oropharyngeal bacterial pathogens. This can be overt as in bacterial pneumonia or bacterial sepsis; or it can be covert when bacterial induced inflammation triggers myocardial infarction or stroke [1 – 3].

I strongly suspect that the same applies to Covid 19. The disease can be asymptomatic, mild or moderate, or severe and potentially fatal. Viral load will be a variable but there are also likely to be bacterial co-factors. The reports from China record indirect evidence of secondary bacterial infection in the form of raised neutrophil counts and raised procalcitonin levels. Most severely affected patients have evidence of sepsis and acute respiratory distress syndrome and nearly all have received high dose parenteral antibiotic therapy [4]. Staphylococcus aureus is a common nasopharyngeal and oropharyngeal bacterial pathogen [5]. Many strains produce pyrogenic toxins and these could cause the cytokine cascade seen in severe cases of Covid 19.

If the public are advised to wear face masks, we must be certain that this will not adversely affect the bacterial flora of the upper respiratory tract. I am not aware of research in adults relevant to this question but there is quite extensive evidence from another field of study in which viral infection interacts with bacterial pathogens to cause sudden death [6]. In the 1980s there were approximately 1,500 deaths per annum in England and Wales from sudden infant death syndrome (SIDS). This condition was associated with prone sleeping and was more common in the winter months when viral respiratory infections were prevalent in the community. Viral respiratory tract infection led to secondary bacterial growth by bacterial pathogens, and toxins produced by the bacteria led to sudden death around 2 to 3 months of age when anti-toxin IgG levels in the infant’s serum were at their lowest levels [6]. Linda Harrison, a PhD student in Lancaster, conducted a study of the nasopharyngeal bacterial flora in infancy [7]. She found that carriage of nasopharyngeal bacterial pathogens (S. aureus, Streptococcus pneumoniae, group A and B streptococcal pathogens, Haemophilus influenzae, and other gram-negative bacilli including Escherichia coli) were increased when infants slept prone and had a viral upper respiratory tract infection (URTI). This was due to a combination of secretions pooling in the upper airways when infants with URTI sleep prone and the fact that infants in the prone position re-breath bacteria growing within the mattress. Moist mucus secretions from the upper airways soaked within the material of the mattress are an effective culture medium for bacterial pathogens.

This is directly relevant to the question of home-made cloth face masks. There is a potential for bacterial pathogens to grow in moist mucus soaked within the material, this could adversely alter the upper respiratory tract flora. Inhalation of bacteria and viruses directly into the lung in patients incubating Covid 19 could then risk synergistic interaction and a rapid deterioration in the patient’s condition.

Those who plan to wear face masks, and there are obvious benefits, should attempt to optimise their oral microbial flora by the regular consumption of natural yoghurt or other fermented milk products (8). Another example of the precautionary principle.

James A Morris, consultant pathologist (retired)
Education Centre, Royal Lancaster Infirmary, Lancaster, UK, LA1 4RP.

1. Morris JA, Harrison LM, Lauder RM. Sudden death from infectious disease. Forensic Pathology Reviews, volume 6, pages 121 – 144, Humana Press, 2011.
2. Price FS. Analysis of urine as a marker of Staphylococcus aureus bacteraemia during intensive care. MSc thesis, Lancaster University, 2013.
3. Bull KL. Analysis of urine for Staphylococcus aureus toxin alpha haemolysin and immunoglobulin as markers of infection. MSc thesis, Lancaster University, 2014.
4. Chen T et al. Clinical characteristics of 113 deceased patients with coronavirus disease 2019: retrospective study. BMJ 2020;368:m1091
5. Morris JA. Staphylococcus aureus bacteraemia: a hidden factor in the pathogenesis of human disease. JSM Microbiology 2017; 5: 1037
6. Morris JA, Haran D, Smith A. Hypothesis: common bacterial toxins are a possible cause of the sudden infant death syndrome. Medical Hypotheses 1987; 22: 211 – 222.
7. Harrison LM, Morris JA, Telford DR, Brown SM, Jones K. The nasopharyngeal bacterial flora in infancy: effects of age, gender, season, viral upper respiratory tract infection and sleeping position. FEMS Immunology & Medical Microbiology 1999; 25: 19 – 28.
8. Morris JA. Optimise the microbial flora with milk and yoghurt to prevent disease. Medical Hypotheses 2018; 114: 13 – 17.

Competing interests: No competing interests

26 April 2020
James A Morris
Consultant Pathologist (retired)
University Hospitals of Morecambe Bay NHS Trust
Education Centre, Royal Lancaster Infirmary, Lancaster, LA1 4RP