Scientists from the Spanish National Research Council (CSIC) have released a report on the current state of knowledge about the transmission of the novel coronavirus in recreational areas used for bathing and other aquatic activities. The report (in Spanish) reviews the available scientific literature to give a series of recommendations.
Out of the potential viral transmission pathways in the recreational waters considered (swimming pools, beaches, rivers, etc.), the main ones would be via respiratory secretions through coughing and sneezing, or when people interact with each other in close proximity (person-to-person contact).
Gatherings of people, common in swimming pools and beaches, as well as shared use of objects are also a mechanism for the spread of the virus. Other potential routes of infection stem from the presence of the virus in wastewater that may end up in bathing waters, and surviving viruses from bathers in water, sand and other surfaces.
Infection by SARS-CoV-2 through contact with water under usual bathing conditions is very unlikely during recreational activities. However, during these activities it is often not possible to maintain the recommended physical distance.
In spas and swimming pools, disinfectants are widely used to prevent microbial contamination of water, and that measure should be enough to inactivate the virus. Regarding aerosols produced in health spas or other facilities with healing waters, the same applies in terms of disinfection. In saunas and steam baths, the high ambient temperature (> 60 degrees Celsius) is expected to reduce viral survival.
Currently there are no data on the survival of SARS-CoV-2 in seawater, but a dilution effect, together with salinity, will probably contribute to decreasing the viral load and to viral inactivation, as it occurs with similar viruses.
Nevertheless, survival of the novel coronavirus would be higher in the water of rivers, lakes and freshwater pools, untreated, in comparison with survival in swimming pools and the sea. They would be the least advisable alternatives in terms of recreational waters, and measures should be taken to avoid large gatherings of people.
Finally, another issue considered is the presence of the virus in sand. In this case, although no empirical studies have been done, the effect of salt from the sea, ultraviolet solar radiation and the high temperature sand may reach would favour pathogen inactivation. The report also emphasises that any potential disinfection of beach sand should be environmentally friendly and the usual procedures used for public urban spaces are not advisable.