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Beach and COVID : What precautions to take for swimming in the sea during the COVID-19 epidemic?

Text updated on 2020-08-26

The risk of contamination COVID at the beach is very low. They occur during interactions with others, mainly out of the water and in the air.

Unfortunately, there are no published studies of the stability of the SARS-CoV-2 coronavirus, the agent of COVID-19. Nevertheless, several observations suggest that the coronavirus does not survive in seawater. Firstly, the envelope surrounding the coronavirus is made up of a layer of lipids, which is poorly resistant to water. Second, even if someone spits in the water, the droplets will be diluted in such a large volume of water that the virus particles will not be in sufficient quantity to infect a person. Third, there have been no cases of contamination COVID through the digestive tract. See the question Can you get coronavirus SARS-CoV-2 from eating?. So don't worry if you drink the cup!

What about the sand? Although there are no studies on the prevalence of viruses in beach sand, the combined action of seawater salt, ultraviolet solar radiation and the high temperature the sand can reach are conducive to the inactivation of coronavirus.

The risks of COVID Contamination at the beach occur out of the water and during interactions with others, mainly through airborne routes, and possibly through indirect contact, via objects that have been contaminated by an infected person. See the question How does COVID-19 get caught?.

The beach is an outdoor area, often well ventilated, but sometimes very crowded. The risk is therefore mainly posed by proximity to others and indirect transmission through contaminated objects.

Here is our advice to make the most of your stay by the sea:

Choose beaches (free or private) that are not very crowded and establishments that respect standards of physical distance and hygiene. Look for apps or sites to reserve your spot in advance and to assess attendance.
Choose a time of day with limited attendance
Carry hydroalcoholic solution and your mask in a plastic bag.
If the temperature is high, especially on sunny days, the coronavirus present on surfaces will be inactivated very quickly, within a few hours (see question Is the SARS-CoV-2 coronavirus resistant to sunlight?) so don't worry about umbrellas and deckchairs used on previous days. On the other hand, pay attention to objects shared without much waiting time between one person and the other: showers, tables, and chairs at the café.
Respect the distances. Be aware of the wind direction and do not stay downwind of people outside your home. Aerosol transmission of coronavirus is similar to the flow of cigarette smoke: imagine that other people are smoking and you don't have to breathe their cigarette smoke.
It is best that your children do not play in close contact with other children.
Prefer remote activities without sharing things.
In beach cafés or restaurants, put on your mask, move away from others, and respect barrier gestures.

Sources

Summary of our knowledge regarding the presence and inactivation of different types of coronaviruses in water. The effect of temperature is also mentioned.

La Rosa, G., Bonadonna, L., Lucentini, L., Kenmoe, S., & Suffredini, E. (2020). Coronavirus in water environments: Occurrence, persistence and concentration methods-A scoping review. Water Research, 115899.

Wiping with towels embedded with soap powder or chlorine is effective in removing the SARS-CoV-2 agent from COVID-19.

Ma, Q. X., Shan, H., Zhang, H. L., Li, G. M., Yang, R. M., & Chen, J. M. (2020). Potential utilities of mask-wearing and instant hand hygiene for fighting SARS-CoV-2. Journal of Medical Virology.

This study shows that simulated sunlight rapidly inactivates SARS-CoV-2 coronavirus suspended in saliva or culture media and then dried on stainless steel. When exposed to UV-B corresponding to sunlight at a latitude of 40°N at sea level on clear days, 90% of the infectious virus was inactivated after 7 minutes in saliva during the summer solstice and after 14 minutes during the winter solstice. These data indicate that natural sunlight can be effective as a disinfectant for contaminated non-porous materials.

Ratnesar-Shumate, S., Williams, G., Green, B., Krause, M., Holland, B., Wood, S., .... Dabisch, P. (2020). Simulated Sunlight Rapidly Inactivates SARS-CoV-2 on Surfaces. The Journal of Infectious Diseases.

99.9% of SARS-CoV-2 coronaviruses are inactivated after 10 days in tap water and 99% after 6 days at 23°C. If the temperature is lower (4°C), the virus is resistant to more than a year in water. Coronaviruses are rapidly destroyed in waste water, with 99.9% of the viruses being inactivated within 2-4 days. This study analysed high virus concentrations and measured, after passage through the water, the presence of RNA but not the infectivity of the virus. It is therefore difficult to transpose the results of this study to a particular situation such as swimming in the sea.

Gundy, P. M., Gerba, C. P., & Pepper, I. L. (2009). Survival of Coronaviruses in Water and Wastewater. Food and Environmental Virology, 1(1), 10.