Before showering in hotels, let the water run to avoid legionellosis.

Legionellosis is considered one of the so-called “rare” diseases, affecting “only” between 12,000 and 20,000 people a year worldwide. However, its mortality rate is very high, around 10% of cases are fatal among those affected. Added to this is the fact that it is an emerging disease, related to the presence of stored and recirculated water, and that this type of installation (accumulators that work with solar panels, “spa” type installations…) is continually increasing. One only has to observe the number of hotels that add the “spa” as an element in their leisure offer. Statistically, the installations that cause the greatest number of illnesses are, in the first place, DHW (domestic hot water) networks with large water accumulation (excluding domestic installations that operate with a small heater), followed by hydro cooling towers and evaporative condensers (a very specific cooling system used to cool large volumes). I had the opportunity to participate in a study for 4 months in a 5 star hotel in the Portuguese Algarve. The purpose of the study was to determine what was more important to avoid the presence of Legionella sp in water networks: the presence of biocide, temperature, or water stagnation. For this purpose, an exhaustive sampling was programmed in 2 different conditions: During the first phase of the study at high chlorine concentrations and temperature. During the second phase at normal temperatures (reaching 50ºC and a minimum of free chlorine residual in cold water). This hotel had one wing of a particular floor without a return network, so the hot water in this particular area did not flow constantly, but had to come from the DHW production branch of the domestic hot water network. The result of the study concluded that water stagnation was more important than chlorine concentration or temperature in the proliferation of the bacteria. Because Legionella sp is mostly found attached to the surfaces of the pipes in the form of a structure called biofilm, the formation of which is favored in conditions of low water flow. It is therefore very important, before taking a shower in a hotel establishment, to let the hot water run for 5 minutes, so that possible traces of Legionella pneumophilla are washed away, thus avoiding the possibility of contracting the disease.

J. M. Berrio