Legionnnaire’s disease alert: cases doubled between 2016 and 2018 in Europe
In 2018, more than 11,300 cases of legionellosis were recorded in the European Union. The people affected were mainly located in Italy, France, Spain and Germany. How can we explain this alarming upsurge of almost 62% compared to 2016? 
Insufficient control standards in Italy
Very often, control is performed too late, in response to the declaration of the first pathological cases of an outbreak. In September 2018, in Brescia, in Italy, it was only after the observation of dozen cases of pneumonia that the Italian health authorities finally ordered checks on the cooling towers of three companies in the region. Nine out of ten samples were found to be contaminated with legionella. By the time these samples were collected and analysed, 405 people were finally hospitalised.
The lack of prevention and of self-checking tests are the main reasons for legionella multiplication in hot water networks and cooling towers.
A 2005 study  already showed that the domestic hot water systems in Italian hotels were heavily colonised by the bacteria. In 75% of the buildings surveyed, 60% of the samples contained more than 10,000 legionella per liter, of which 87% were Legionella pneumophila, responsible for legionellosis. For the record, the regulatory threshold not to be exceeded is of 1000 bacteria per liter. This clearly reflects the inadequacy of control and prevention measures implemented in some countries, particularly in Italy. On the other hand, in other countries such as the United Kingdom, Germany or France, oversight measures are much more stringent.
A vulnerable ageing population: Italy, Greece and Germany most at risk
Italy, Greece and Germany are the countries with the highest proportion of older people (aged 65 and over) in the population. As a matter of fact, it is precisely the elderly or immunosuppressed individuals who incur the greatest risks of developing severe symptoms of legionnaire’s disease, which can lead to death. Young and healthy people are more resistant, resulting in fewer cases in countries with a lower average age.
The general ageing of the population in Europe implies an even greater threat in the future if no action is taken in time.
Industrialisation multiplies the risks in Western Europe
Legionella grow particularly fast in artificial water systems. Air cooling towers (ACT) and hot sanitary water (shower, bath, tap) are major breeding grounds and therefore at-risk areas.
A much higher industrialization rate in Western Europe implies a very large number of ACTs and installations projecting aerosols, micro-droplets of water invisible to the naked eye that can be contaminated by the bacteria.
Massive use of air-conditioning devices in Southern Europe
Southern Europe, due to its Mediterranean climate, shows higher demand for collective and individual cooling devices such as air conditioners and mist coolers. Italy, Spain, Greece and France account for the majority of European sales of this kind of equipment.
Climate, a decisive factor in the proliferation of legionella in western and southern countries
Southern countries have an additional aggravating factor in the development of the bacterium.
Legionella thrives in warm environments, i.e. in the 25-45 °C range. Therefore, countries where the temperature regularly exceeds 25 °C present an increased risk of contamination. The “cold” water system can easily reach the threshold for these bacterium to proliferate and generate infections.
To some extent, the increase in heat waves due to global warming could also explain the rise in legionellosis cases, particularly in France, the Netherlands and Germany. Heat waves episodes, such as in June 2018 in France, are noticed to be correlated with outbreak peaks.
An absence of data that distorts interpretations for the poorest European countries
Greece, Romania, Estonia: a worrying under-diagnosis of legionellosis
According to the European Centre for Disease Prevention and Control (ECDC) , there is a concerning under-diagnosis of legionellosis in Greece, while countries such as France and Italy have put in place mandatory reporting measures that explain their top incidence rankings. For example, until very recently, most legionellosis cases contracted in Greece had been diagnosed in tourists home counties, after their return. But the disease was still very rarely reported among the Greek population. In addition, datas on legionella are almost non-existent for some countries such as Romania or Estonia.
In general, all throughout Europe, the disease remains largely under-diagnosed. Apart from the recorded cases of legionellosis, it should be kept in mind that the disease is not systematicllay reported, especially in cases of spontaneous recovery. As the symptoms of legionellosis are very similar to those of influenza during the fisrt stages, both diseases are often confused.
Multiple parameters converge to a single key priority: prevention
Ageing of the population, global warming, industrialization rate and its associated constant development of water networks and at-risk facilities involving the projection of aerosols are all main factors that explain the dramatic growth in cases of legionellosis in the last recent years in Europe and their uneven distribution over the territory.
Greater awarness has led some national health authorities to take measures and to make the disease mandatory to report. It is the case in France since 1987. But is this enough to face the risk?
To date, there is no vaccine or preventive treatment against the disease. Fighting legionnaire’s disease requires implemeting simple prevention actions, such as conducting regular self-monitoring tests. These tests are essential to anticipate the risk and act quickly in the event of contamination. There are now innovative, easy to use and cost-effective solutions that can be carried out on site or at home in complete autonomy. Fast and reliable, they make it possible to control the legionella risk for any installation.
 Borella P, Montagna MT, Stampi S, et al. Legionella contamination in hot water of Italian hotels. Appl Environ Microbiol. 2005;71(10):5805–5813. doi:10.1128/AEM.71.10.5805-5813.2005 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1265926/
  European Centre for Disease Prevention and Control, 2019, https://ecdc.europa.eu/en/home
European Commission, COMMISSION STAFF WORKING DOCUMENT Review of available information Accompanying the document Communication from the Commission to the European Parliament, the Council, the European Economic and Social Committee and the Committee of the Regions on an EU Strategy for Heating and Cooling, Février 2016, https://ec.europa.eu/energy/sites/ener/files/documents/1_EN_autre_document_travail_service_part2_v6.pdf
Legionella Colonization of Hotel Water Systems in Touristic Places of Greece: Association with System Characteristics and Physicochemical Parameters Maria A. Kyritsi 1 , Varvara A. Mouchtouri 1, Antonis Katsioulis 1,2, Elina Kostara 1 , Vasileios Nakoulas 1 , Marina Hatzinikou 1,2 and Christos Hadjichristodoulou 1,2,*
Source cover image: European Centre for Disease Prevention and Control, https://ecdc.europa.eu/en/legionnaires-disease/surveillance/atlas, on July 3rd 2019
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