Bacteria, drowning... Should you swim in a pool or in white water?

Wild bathing has grown considerably in recent years

Bacteria, drowning... Should you swim in a pool or in white water?

Wild bathing has grown considerably in recent years. Not only is outdoor swimming a pleasant way to enjoy the sun, fresh air and green surroundings as the heat returns, but it can also help relieve stress and increase our endorphins, hormones linked to the feeling of pleasure. This helps to create a feeling of well-being, while burning a few calories by working our muscles.

But with the joys of outdoor swimming come some dangers... Not only are "wild" swimmers more exposed to tides, currents and swells, but there can also be harmful insects and other microbes in the pool. water. And with untreated sewage regularly pouring into seas, rivers and lakes, it can be difficult to find a safe place to splash around.

Of course, swimming in a pool comes with its own set of risks, which are usually well identified: urinary tract infections, ear infections and other stomach ailments (gastro, etc.) are the most common ailments you can get there. catch.

Poorly maintained pools can also cause irritation, stinging eyes and harbor all kinds of bacteria and fungal germs as well as urine, feces or even sweat – all of human origin. In many ways, therefore, swimming pools are reminiscent of a large bathhouse filled with unsavory intruders.

But while it's obvious that swimming in outdoor waters carries different risks than swimming in a pool, the question of where it's safest to swim doesn't necessarily seem obvious... So what to focus on: swimming pools , or rivers, lakes, canals and seas?

Unlike swimming pools, whose waters are carefully controlled, outdoor waters constantly change composition. This means that chemicals can seep into it from neighboring farms or industrial areas.

But wild waters can also "host" animal droppings as well as human sewage - which may or may not be dumped there legally: if you see pipes nearby, use your common sense: don't go there not.

Vigilance is therefore required, because there are not always signs indicating local dangers… and the presence of toxic agents is not necessarily obvious. If in doubt about the chemical safety of outdoor waters, it is best not to enter them. If the water doesn't look clear or smell good, for example, again trust your instincts.

Outdoor waters also present natural risks compared to swimming pools, especially in summer. Blue-green algae - or cyanobacteria - are a type of bacteria found naturally in lake ecosystems. During hot summers, they tend to multiply and form a greenish scum on the surface of lakes. This blue-green algae bloom can release toxins that are harmful to humans and sometimes deadly to pets, so don't let your dog bathe or drink in it.

Diarrhea is the most common illness linked to swimming in open water, often due to its contamination by sewage. You get sick if you swallow contaminated water containing bacteria and viruses such as E. coli and Norovirus, respectively.

Rats living in sewers adjacent to rivers or freshwater canals may also carry the pathogenic bacterium Leptospira, which causes Leptospirosis (Weil's disease), in their urine. Infection occurs when soil or water from a lake, river or canal, containing urine of infected animals, is swallowed, comes into contact with the eyes of a swimmer or with a cut.

Leptospirosis can cause liver and kidney damage and can be fatal if left untreated. If you have symptoms of flu or jaundice up to two weeks after swimming in a river or canal, it may be a good idea to ask your doctor to test you for leptospirosis.

As for the sea, a 2018 study found that bathers were more likely to suffer from infections of the ear, nose, throat and gastrointestinal system than people who stayed on the beach. It is therefore advisable to wash after swimming in outdoor waters, especially before eating...

If we take into account, even if it is possible that people relieve themselves in a swimming pool, in particular public ones, these basins, which are very popular, will almost always be a safer environment for swimming... Especially if we take into account , in addition, jellyfish stings or additional risks of swimming in cold water. Wild swimmers are more likely to feel bad when swimming in outside water (temperature difference…) and there will always be pathogenic microbes potentially present.

Considering these different parameters, it is possible that an outdoor pool actually offers the best of both worlds: bathing with the sun in a controlled and safe sanitary environment...

* Dr Primrose Freestone is Associate Professor of Clinical Microbiology in the Department of Respiratory Sciences at the University of Leicester (UK). She is a biochemist by training, with extensive experience in bacterial physiology and biochemistry.