The sun and good weather make beaches and pools an attractive destination, but is it safe to swim in times of pandemic?
As summer approaches in the northern hemisphere and many places in Latin America are still enjoying good weather, pools and beaches begin to open.
Health authorities have warned that the summer will slow down, although No to stall, the coronavirus pandemic in countries that are entering the hottest seasons.
Hence many wonder if the disease can be transmitted or infected ThroughWater, the sand or grass that usually surrounds pools.
Since there are no specific studies of the survival of covid-19 in aquatic environments, the World Health Organization (WHO) has based its recommendations on the subject on scientific evidence collected for other coronaviruses.
"The morphology and chemical structure of this virus is similar to that of other coronaviruses for which there is survival data,” says its report.
In fact, the agency remembers, for example, that it was determined that the influenza virus died alone five minutes after being in contact with drinking water with a residual chlorine of 0.3 milligrams per liter.
“Although the presence of covid-19 in untreated water is possible, has not been detected in drinking water supplies,” the Pan American Health Organization (PAHO) explains to BBC Mundo.
But what happens to sea water and he of the swimming pools?
The Higher Council for Scientific Research (CSIC) of Spain issued a report this week in which it analyzes the probabilities of infection in these environments.
The chlorine used as a disinfectant in swimming pools facilitates the death of the coronavirus that causes covid-19.
Its use has been mandatory in many countries due to health regulations for years.
“There are many uncertainties around this issue,” Joan Grimalt, a researcher at the Institute of Environmental Diagnostics and Water Studies of Spain, explains to BBC Mundo.
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“Contamination within the water is unlikely, but it is much more unlikely in salt water or pool water", Add. The percentage of chlorine that a pool should have is at least 0.5 milligrams per liter.
Although they usually have between 1 and 2 milligrams per liter, a level that, according to sector authorities, remains safe for health.
“You don't need more chlorine, but you have to make sure that the pool always has the adequate level,regardless of the number of people swimming,” says the researcher.
The United States Centers for Disease Control and Prevention (CDC) agree that “the proper operation and maintenance (including disinfection with chlorine or bromine) of swimming pools, hot tubs, spas or water play areas should inactivate the virus.”
The Spanish CSIC recommends washing “your face and hands with soap before getting into the pool” and insists that is the public gathering at swimming pools or beaches which can put people at risk.
“Sea water has salt and it has been experimentally proven that this element deactivates or destroys covid-19,” says Grimalt. But this is “very normal,” he emphasizes. It happens with many viruses.
“There are many organisms that cannot live in a saline environment. Sea water has osmosis, a density of ions, which kills many of the virus families.”
What happens in the case of the one that causes covid-19 is that it is composed of a core of genetic material and a protein capsid that surrounds it and, like other respiratory coronaviruses, it is covered by a lipid envelope.
Other viruses, such as Hepatitis A, For example, they lack that envelope.
“Surprisingly, this makes them last longer in fresh water or seawater than covid-19,” which dies faster, explains Grimalt.
To the reaction to sea salt we must add the “dilution effect”.
That is, the virus spreads in water and this reduces its power of infection.
“To become infected, a person needs to be exposed to a number minimum viral particles“explains Bruce Ribner, medical director of the Serious Communicable Diseases Unit at Emory University Hospital, in the United States.
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“Any discharge that goes into the water, like from a sneeze or cough, it will dilute quickly,” he says.
“This would make the probability of a person being exposed to minimal amount of viral particles required to cause infection is very small and, in a real-life situation, too small to be worried about,” he adds.
However, the way in which the virus could reach the sea is not only through an asymptomatic bather who is on the beach.
In the case of covid-19, the main risk is wastewater from cities that flows at sea.
The CSIC report warns that there is still no evidence on the infectivity of the virus (the ability of a pathogenic agent to invade an organism and cause an infection) in wastewater, where it does. traces of the new coronavirus have been found.
"This possibility cannot be completely ruled out because there are already three studies in which the presence of the infectious virus is described in stool samples from infected patients,” it reads.
So If the beach is near a collector, you have to be careful.
“The treated or wastewater that reaches the sea can contain covid-19 because the feces of sick or asymptomatic people have a high concentration of viruses,” says Grimalt.
But a report from the Center for Sustainable Water and Energy Technologies at the University of Arizona explains that “research also suggests that coronaviruses are more sensitive to water and wastewater treatment processes than their non-enveloped virus counterparts.” .
“Therefore, these processes probably provide adequate protection against coronaviruses” and should be enough, explains the document.
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There are three factors that contribute to making the transmission of the new coronavirus in the arena difficult: sun, salinity and surface roughness.
The ultraviolet light from the sun destroy the virus in the sand.
But we also have to take into account that the sand has high concentrations of salt from the sea that bathes it.
Furthermore, “sand is not a smooth surface. What has been seen is that coronaviruses remain for less time on rough surfaces,” says Grimalt.
“The probability that contaminated sand will lead to infection is surely too small to be a realistic concern“, believes Dr. Ribner.
Water from rivers, lakes or streams
If we want to go swimming in rivers, lakes and waters with little circulation, its use is highly discouraged.
In these environments it is necessary take extreme precautionary measures. These aquatic environments are the most inadvisable for recreational use compared to other alternatives.
“Studies focused on other coronaviruses, with characteristics similar to SARS-CoV-2, have shown that viruses remain temporarily infectious in natural freshwater environments“says the CSIC report.
“In principle this virus is not infectious through water, but given the choice, if one wants to be sure, it is better to swim in places where it is clear that there is no possibility of infection and those are swimming pools and the sea,” Grimalt concludes.