Faecal shedding of SARS-CoV-2: considerations for hospital settings.

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.