Sir,
The recent opinion article by McDermott and colleagues offers important considerations for potential faecal bio-aerosolization transmission in hospital settings [1]. Several recent findings have been referenced that have strengthened the plausibility of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) faecal shedding as a mode of transmission and well-considered research questions are raised on the matter of bio-aerosols. The authors may have overlooked some pressing priorities with potentially far-reaching consequences.
In hospital settings, extra care is warranted in the handling of faecal wastes, regardless of whether individuals are infected, recovering, or have recovered. A study by Wang et al. following the 2002–2003 SARS outbreak adopted biochemical analysis to ascertain the plausibility of sewage as a transmission route of the coronavirus implicated in the outbreak (SARS-CoV-1) [2,3]. An electropositive filter media particle was used to concentrate SARS-CoV-1 from the sewage of hospitals, with SARS-positive patients. Detection and identification using cell culture and reverse transcription–polymerase chain reaction followed. Sewage discharged by two hospitals was found positive for SARS-CoV-1. A recent study with similar methodological design identified positive samples of the novel coronavirus (SARS-CoV-2) in hospital inlets of the preprocessing disinfection sewage pool, although not in the final outlet [4]. However, this study had significant limitations and the time lag that faecal testing represents, in comparison to other forms of testing, should be recognized [5]. Careful management of sewage discharged from hospitals is a priority in the preventive approach to COVID-19 even if the evidence base is not yet developed.
Regarding aerosol transmission of SARS-CoV-2, toilet plumes are known to disperse microbes to the immediate environment and the extent of dispersion can be modelled using the inverse-square law. In hospital settings, heightened care for disinfection is necessary in toilet cubicles; unnecessary fomites with the potential to harbour faecal microbes in the surrounding environment should be removed. A common example of an overlooked fomite around household toilets are toothbrushes, particularly when positioned in relatively close proximity to toilets [6]. The strengthening plausibility of faecal–oral transmission presents a challenge for this pathway. Hand dryers also present the risk of generating bio-aerosols, with some modern designs accommodating an upward airstream of microbes more readily. This may pose an increased risk of pathogen inhalation or entry through the conjunctiva: a recently identified mode of entry [7].
In the preventive approach to this unqualified – albeit highly plausible – mode of transmission, it is necessary to reinforce existing advice for hand hygiene with emphasis on hand washing after using a toilet, and reminding users to close toilet lids when flushing. Effective sewage management is essential for public health reasons and environmental consideration.
Conflict of interest statement
None declared.
Funding sources
None.
References
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