Extreme heat and air conditioning: what is legionellosis, this potentially fatal disease?

When outside temperatures exceed 35°C or even 40°C, as was recently the case in France, air conditioning systems are sometimes life-saving. However, they are not without risk. Thermal shock is one of them, but air conditioning is also a source of respiratory infections, which are sometimes serious.

The purpose of air conditioning systems is to cool indoor air. But they are not safe for health. Indeed, if the cooling of the air is too great, the risk of thermal shock is real. But it’s not the only one. When you go too often from hot to cold, for example, the mucous membranes – particularly the respiratory ones – become irritated. Therefore they are more likely to be infected by viruses or other bacteria causing colds and angina in particular. Not to mention that air conditioning dries the air, and therefore the respiratory mucous membranes.

Additionally, when air conditioning systems are not maintained properly, they can harbor microbes themselves which they release into the cooled air. Again increasing the risk of contaminating the occupants of the room concerned.

The risk of legionellosis

Even more serious: legionellosis. This disease of bacterial origin, potentially fatal, exposes to an acute pulmonary infection. The bacteria in question, called Legionella, “are part of the aquatic flora and are found in many hot freshwater sources”, describes the Institut Pasteur.

So what does this have to do with air conditioning? Some systems, widely used in hotels, hospitals and other large establishments, are based on water for air cooling. However, if this water is contaminated by these bacteria, they take advantage of relatively high temperatures in the system itself to proliferate. Contamination then occurs by inhaling micro-droplets of water expelled into the air. It is the regular maintenance of the systems that reduces the risk of contamination.

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