This paper provides another review of the published scientific literature on coronaviruses in water (including wastewater, environmental waters and drinking water). The focus, in this case, is on the survival of viable infectious virions in these environments, very much from a public health perspective.
A key observation is that there have been very few studies undertaken to investigate the fate of coronaviruses in water. The authors found that since 1978 only 22 studies have met the inclusion criteria for this review (which is more than the 12 studies that met the inclusion criteria for a similar literature review by La Rosa et al. (2020)).
A general observation was that human coronaviruses have rarely been detected in field investigations. This may be a consequence of their short environmental survival in water. However, it may also be related to their poor recovery in analytical methods most commonly applied to detect viruses in water. A further factor has been a general lack of research interest on this topic, as a consequence of broad acceptance that significant survival of these enveloped viruses is unlikely.
Studies undertaken in controlled laboratory environments have shown that human coronaviruses can survive in water for several days at cold temperatures (4 oC), but are less persistent at warmer temperatures. Their ability to persist in water environments does appear to be much more limited than non-enveloped viruses more generally associated with waterborne disease.
Given the stated focus on “persistence” and public health implications, this paper doesn’t significantly address the related issue of monitoring residual SARS-CoV-2 RNA for the purpose of wastewater-based epidemiology. However, many of the recent published papers and pre-prints that have been focused on this topic are summarised under the heading of “environmental monitoring studies”.
The authors don’t make any incorrect statements, but the paper is missing a clear distinction here about what is evidence for viable environmental virions and what is evidence for nothing more than residual fragments of RNA in water. Clearly pointing out that distinction would help to prevent potential public misunderstandings about the implications of these observations.
The authors conclude that the scarcity of information on the presence and persistence of coronavirus in the environment merits urgent research, which should include the following topics:
- Efficient methods to concentrate and detect enveloped viruses (and coronavirus in particular) from water matrices;
- Survival of these viruses in natural conditions, at different temperatures and in different types of water;
- Efficiency of water treatment processes (including disinfection) to avoid contamination from urban and hospital wastewater;
- Implications for water reuse for agriculture including the possibility of food (raw vegetables) contamination;
- A surveillance system through sewage monitoring of the potential virus circulation.
Carducci, A., Federigi, I., Liu, D., Thompson, J. R. and Verani, M. (2020) Making Waves: Coronavirus detection, presence and persistence in the water environment: State of the art and knowledge needs for public health. Water Research, 179, 115907.