Category Archives: Cooling Towers

ECDC – Legionnaires’ disease – Annual Epidemiological Report for 2020


ECDC’s annual surveillance reports provide a wealth of epidemiological data to support decision-making at the national level. They are mainly intended for public health professionals and policymakers involved in disease prevention and control programmes.

Executive summary

  • Legionnaires’ disease remains an uncommon and mainly sporadic respiratory infection with an overall notification rate of 1.9 cases per 100 000 population for the EU/EEA in 2020.
  • A small decrease in the annual notification rate was observed, down from the 2.2 cases per 100 000 population reported in 2019.
  • Notification rates remained heterogenous across the EU/EEA, varying from fewer than 0.5 cases per 100 000 population to 5.7 cases per 100 000 population, with the highest rate reported by Slovenia.
  • Four countries (France, Germany, Italy and Spain) accounted for 72% of all notified cases.
  • Males aged 65 years and older were most affected (7.1 cases per 100 000 population).
  • The number of reported cases to the travel-associated surveillance scheme decreased by 67% in 2020 compared with 2019.
  • Only 10% of cases were culture confirmed (10%), likely leading to underestimation of disease caused by Legionella species other than Legionella pneumophila.

Research – Innovative Antibiofilm Smart Surface against Legionella for Water Systems


Legionella pneumophila contamination of water systems is a crucial issue for public health. The pathogen is able to persist in water as free-living planktonic bacteria or to grow within biofilms that adhere to and clog filters and pipes in a water system, reducing its lifespan and, in the case of hospital buildings, increasing the risk of nosocomial infections. The implementation of water management is considered to be the main prevention measure and can be achieved from the optimization of water system architecture, notably introducing new materials and strategies to contrast Legionella biofilm proliferation and so prolong the water system functionality. In this research, we propose a new smart surface against L. pneumophila biofilm formation. This is based on an innovative type of coating consisting of a sulfonated pentablock copolymer (s-PBC, commercially named Nexar™) deposited on top of a polypropylene (PP) coupon in a sandwich filter model. The covering of PP with s-PBC results in a more hydrophilic, acid, and negatively charged surface that induces microbial physiological inhibition thereby preventing adhesion and/or proliferation attempts of L. pneumophila prior to the biofilm formation. The antibiofilm property has been investigated by a Zone of Inhibition test and an in vitro biofilm formation analysis. Filtration tests have been performed as representative of possible applications for s-PBC coating. Results are reported and discussed.

Research – Rising Incidence of Legionnaires’ Disease and Associated Epidemiologic Patterns, United States, 1992–2018



Reported Legionnaires’ disease (LD) cases began increasing in the United States in 2003 after relatively stable numbers for >10 years; reasons for the rise are unclear. We compared epidemiologic patterns associated with cases reported to the Centers for Disease Control and Prevention before and during the rise. The age-standardized average incidence was 0.48 cases/100,000 population during 1992–2002 compared with 2.71 cases/100,000 in 2018. Reported LD incidence increased in nearly every demographic, but increases tended to be larger in demographic groups with higher incidence. During both periods, the largest number of cases occurred among White persons, but the highest incidence was in Black or African American persons. Incidence and increases in incidence were generally largest in the East North Central, Middle Atlantic, and New England divisions. Seasonality was more pronounced during 2003–2018, especially in the Northeast and Midwest. Rising incidence was most notably associated with increasing racial disparities, geographic focus, and seasonality.

Research – Legionellosis: A novel mechanism by which the bacterium Legionella pneumophila regulates the immune response of its host cells

Science Daily

Legionellosis or Legionnaires’ disease affected more than 1 800 people in France in 2019 and caused 160 deaths. This emerging disease is caused by Legionella pneumophila, an environmental bacterium that thrives in hot water systems. Researchers have discovered a mechanism that allows Legionella pneumophila to target the immune response of the cells it infects by secreting a small regulatory RNA. This mechanism, not described before, facilitates the survival and proliferation of Legionella pneumophila during infection. The work provides precious information on the strategies used by bacteria to manipulate their host cells.

Research – Emerging Legionella species data



08 February 2022

Article: 56/502

In July 2021, the Legionella Control Association (LCA), in conjunction with the Health and Safety Executive (HSE), Public Health England (PHE) and local authorities, held a webinar aimed at raising awareness of increasing Legionella positivity rates post lockdown.  The data demonstrated that the average positive rate in the UK had increased by around 2% following the lockdowns in response to COVID-19.

To investigate if there were particular species that could have led to this increase, LCA approached the three commercial laboratories in the UK that use MALDI-ToF to confirm down to species level, and asked if they would share their data. This information has now been returned by some laboratories, with findings from over 70,000 positive result samples in a two-year period revealing:

  • over 53% of the results were L.anisa
  • over 32% of the positives were L. pneumophilia, both SeroGroup 1 and SeroGroup 2-15
  • nearly 1% of positives were for L. rubilucens
  • over 6.5% of the results did not confirm a species type
  • there were over a dozen other species identified in results that accounted for less than 1% of the data set

The first line clinical diagnostic tool used to confirm Legionnaire’s disease in the UK is commonly a urinary antigen test (UAT), and this method looks predominantly for L. pneumophilia SeroGroup 1. Given the data LCA has provided so far, this could potentially mean missing over 70% of Legionella infections in patients. It should be highlighted that this data is in its infancy, and LCA state that further research needs to take place before any significant changes are considered or undertaken.

Source: LCA, January 2022

Germany – Legionnaires’ disease sickens five, kills 2 in Heilbronn

Outbreak News Today

CDC legionella

In Heilbronn District, in northern Baden-Württemberg, Germany, it is reported that five men and women have contracted Legionnaires’ disease and two have died.

The patients came from Obersulm, Ellhofen, Weinsberg and Löwenstein, health officials announced. Most of them are middle-aged and older men. The two deceased men had a previous illness and were 49 and 81 years old.

Health authorities are feverishly looking for the source of the contamination.

Experts from the Heilbronn health department are not assuming that contaminated drinking water is the cause of the infections. The sick lived in different places, there are several water suppliers. “The surrounding sewage treatment plants were also sampled,” said a spokeswoman for the dpa office. “We assume that the cause can be found in an evaporative cooling system.” The health department fears that there may be more cases.

Research – Legionella and Biofilms—Integrated Surveillance to Bridge Science and Real-Field Demands



Legionella is responsible for the life-threatening pneumonia commonly known as Legionnaires’ disease or legionellosis. Legionellosis is known to be preventable if proper measures are put into practice. Despite the efforts to improve preventive approaches, Legionella control remains one of the most challenging issues in the water treatment industry. Legionellosis incidence is on the rise and is expected to keep increasing as global challenges become a reality. This puts great emphasis on prevention, which must be grounded in strengthened Legionella management practices. Herein, an overview of field-based studies (the system as a test rig) is provided to unravel the common roots of research and the main contributions to Legionella’s understanding. The perpetuation of a water-focused monitoring approach and the importance of protozoa and biofilms will then be discussed as bottom-line questions for reliable Legionella real-field surveillance. Finally, an integrated monitoring model is proposed to study and control Legionella in water systems by combining discrete and continuous information about water and biofilm. Although the successful implementation of such a model requires a broader discussion across the scientific community and practitioners, this might be a starting point to build more consistent Legionella management strategies that can effectively mitigate legionellosis risks by reinforcing a pro-active Legionella prevention philosophy. View Full-Text

EU – Legionnaires’ disease – Annual Epidemiological Report for 2019



ECDC’s annual surveillance reports provide a wealth of epidemiological data to support decision-making at the national level. They are mainly intended for public health professionals and policymakers involved in disease prevention and control programmes.

Executive summary

  • Legionnaires’ disease remains an uncommon and mainly sporadic respiratory infection with an overall notification rate in 2019 for the EU/EEA of 2.2 cases per 100 000 population.
  • There is heterogeneity in notification rates between EU/EEA countries, with the highest rate reported by Slovenia (9.4 cases per 100 000 population).
  • The annual notification rate increased in recent years, from 1.4 in 2015 to 2.2 cases per 100 000 population in 2019.
  • There was a marginal decrease of less than 1% in the number of reported cases in 2019, compared with 2018.
  • Four countries (France, Germany, Italy, and Spain) accounted for 71% of all notified cases in 2019.
  • Males aged 65 years and above were most affected (8.4 cases per 100 000 population).
  • Only 10% of cases were culture-confirmed (10%) probably meaning that disease caused by Legionella species other than Legionella pneumophila is under-estimated.

Denmark – Legionnaires’ disease in Denmark in 2020


Legionella_Plate_01    CDC legionella

278 cases of legionnaires’ disease were detected in Denmark in 2020. Of these, 94.6% had been infected in Denmark. That is the highest number ever.

The Statens Serum Institut (SSI) has issued the annual report on how many cases of Legionnaires’ disease (LS) were found in Denmark in 2020.

A total of 278 cases of LS, also known as legionella pneumonia, were detected. Of these, 165 were men (59.4%) and 113 women (40.6%).

Out of these, 39 patients died within 30 days after the disease had broken out or they had been hospitalized. It gives a mortality rate of 14%.

Almost 95% infected in Denmark

Out of the 278, 263 people were infected in Denmark. This corresponds to 94.6%. This is an increase of 25% compared to the average for the last three years, and thus the highest number ever.

“The increase in the number of infected in Denmark may be related to a higher test activity in 2020. It may be due to the fact that many hospitalized patients with suspected covid-19 have also been examined for legionella infection,” says head of department Søren Anker Uldum from SSI.

15 infected on travel

There are only 15 cases (5.4%) where people in 2020 were infected with LS when traveling abroad. In 9 cases, it was while traveling in Europe. 5 were infected while traveling in Asia and 1 traveling to the American continent.

The proportion of travel-related LS cases is usually 20-25%

“Due to the extensive travel restrictions in 2020 due to the Covid-19 pandemic, there has been very limited travel activity. This is probably the reason for the few travel-associated legionella cases in 2020 ”, says Søren Anker Uldum.

Read more

You can read more about Legionnaires’ disease here.

You can also see the annual statement for legionnaires’ disease in Denmark in 2020 here .

Legionella risks during the coronavirus pandemic



Employers, the self-employed and people in control of premises, such as landlords, have a duty to protect people by identifying and controlling risks associated with legionella.

If your building was closed or has reduced occupancy during the coronavirus (COVID-19) pandemic, water system stagnation can occur due to lack of use, increasing the risks of Legionnaires’ disease.

You should review your risk assessment and and manage the legionella risks when you:

If the water system is still used regularly, maintain the appropriate measures to prevent legionella growth.

You can find out what Legionnaires’ disease is, where it comes from, how people get it and symptoms and treatment by reading our guidance What is Legionnaires’ disease?.