COVID-19: The environmental implications of shedding SARS-CoV-2 in human faeces

At a time when the world is so focused on the respiratory pathways of a respiratory virus, this recent paper in Environment International argues that understanding the opportunities for SARS-CoV-2 to be spread by the faecal-oral route must not be neglected. They state that the public health implications of significant concentrations of SARS-CoV-2 arriving at sewage treatment plants, and the consequent discharge into the wider environment are only just beginning to be investigated.

As previously documented on this blog, coronaviruses can remain viable in sewage for up to 14 days depending on the conditions such as temperature. However, the presence of solvents and detergents in wastewater can compromise the viral envelope.

The authors of this paper argue that although there is not yet any robust evidence for coronaviruses being directly transmitted by the faecal-oral route, the increase of viral load in the environment could increase potential human exposure. In particular, the transport of coronaviruses in water increases the potential for the virus to become aerosolised, particularly during the pumping of wastewater through sewerage systems and at the sewage treatment plant, and during its discharge and subsequent transport through the catchment drainage network.

Other situations where there is increased risk of human exposure from wastewater include high rainfall events which exceed sewage infrastructure capacity, resulting in discharge from combined sewer overflows and sewer flooding. The risk of exposure via the faecal-oral route is also of particular concern in parts of the world where safely managed sanitation systems are limited, and particularly where there are high levels of open defecation or other forms of non-sewered sanitation.

REFERENCE:

Quilliam RS, Weidmann M, Moresco V, Purshouse H, O’Hara Z and Oliver DM (2020) COVID-19: The environmental implications of shedding SARS-CoV-2 in human faeces. Environment International, 140, 105790.

https://doi.org/10.1016/j.envint.2020.105790

Published by Stuart Khan

Professor of Civil & Environmental Engineering, University of New South Wales

2 thoughts on “COVID-19: The environmental implications of shedding SARS-CoV-2 in human faeces

  1. Hi Stuart
    I think it is important to remember that the survival studies done with SARS in sewage had to spike cultured SARS into the sewage because culturable virus was not detected in sewage from a specialist hospital treating SARS patients (virus RNA present, but not culturable virus). At room temperature the spiked SARS only retained infectivity in sewage for 2 days in that study.

    In the case of COVID-19, the available data suggests that the number of infectious SARS-CoV-2 in faeces is extremely low (there is a single study that used 2 rounds of cell culture to demonstrate the presence of infective virus, whereas other papers could readily culture virus from sputum but not faeces when virus concentrations were similar in the two sample types). There is also a study using intestinal enteroids showing that these organoids can be infected by SARS-CoV-2 but the released viruses are rapidly inactivated by cell secretions (intestinal secretions), which provides a mechanism for how virus in faeces are inactivated. Of course, there may be nasal / mucosal secretions that also end up in sewage, but I am not sure how much that contributes to virus load in sewage.

    Unless there is evidence of infectious virus in sewage, these types of papers are speculative and possibly risk diverting research funding from where it will do more benefit in the COVID area

    Cheers

    Paul

    Liked by 1 person

  2. Completely agree with Paul – this paper is really very disappointing. In my mind it sets back the debate and diverts attention, while also causing undo panic amongst treatment plant operators. There have been no reported cases associated with contact with wastewater.

    Liked by 2 people

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