Legionnaires' disease: EAWAG launches project to combat Legionella in buildings
Cases of Legionnaires' disease are increasing in Switzerland: 582 cases of the severe pneumonia were registered by the Federal Office of Public Health (FOPH) last year. In 2013, there were half as many. Despite antibiotic treatment, the disease leads to death in five to ten percent of those affected.
The pathogenic bacteria of the so-called Legionnaires' disease are called Legionella. They are found, among other things, in water. Inhalation of finely atomized, contaminated water droplets is dangerous. This can happen wherever such droplets are produced: in car washes, recooling units of air conditioning systems or industrial cooling towers. Under certain circumstances, however, legionella can also form in drinking water.
This makes fountains, steam baths and showers a potential source of infection.
Pathogens in buildings
But how do the pathogens actually get into the building installations? In central drinking water treatment plants that supply municipalities and cities, most bacteria and nutrients are removed from the water. Concentrations also remain low in the distribution network, the pipes that bring drinking water to buildings. "But then it becomes problematic," explains Frederik Hammes of the Environmental Microbiology Department at the Eawag Water Research Institute. This is because water is heated in buildings, and this can cause legionella to form in the hot water pipes of domestic installations. The pathogens grow optimally at water temperatures of between 35 and 40 degrees Celsius. It is true that legionella can be killed by heating the hot water to 60 degrees Celsius. However, this temperature is seldom reached at shower heads, for example.
In addition, in order to save energy, boilers in many buildings remain below 60 degrees. Legionella can also multiply in cold water pipes, however, if the water regularly heats up to higher temperatures. Other factors, such as nutrient input through plumbing materials and irregular or lack of water exchange, are also known to promote proliferation. However, many questions remain unanswered: for example, exactly how Legionella occurrence and human infection are related, or how drinking water pipes can be most effectively tested for Legionella.
For this reason, the Swiss Federal Food Safety and Veterinary Office (FSVO), the Swiss Federal Office of Energy (SFOE) and the Swiss Federal Office of Public Health (SFOPH) are now funding the four-year multidisciplinary project "Legionella control in buildings" (LeCo), led by Eawag, to the tune of CHF 2.5 million. In addition to Frederik Hammes' Drinking Water Microbiology research group, the project involves the Lucerne University of Applied Sciences and Arts (HSLU), the Swiss Tropical and Public Health Institute (Swiss TPH), the Cantonal Laboratory Zurich (KLZH) and the Eawag research group "Pathogens and Human Health" led by Tim Julian.
Julian, together with Swiss TPH, wants to know how many Legionella in shower water lead to how many cases of illness. Specifically, the researchers want to use a mathematical model to calculate the probability of infection at different Legionella concentrations.
Another focus of the project is to improve sampling. This is because a regulation has been in force since 2017, according to which publicly accessible showers must not contain more than 1,000 Legionella bacteria per liter of water. But the bacterial composition in a drinking water installation varies, making sampling laborious. "In order to increase the informative value and comparability of the samples, we need to optimize and standardize the collection process," says Franziska Rölli from the Institute of Building Technology and Energy at HSLU.
"Awareness-raising and education also play an important role. This is because experts from the fields of architecture, specialist planning, sanitary installation and building operation are often not sufficiently familiar with the legionella issue. That's why, in addition to research activities, the project consortium attaches great importance to passing on the newly acquired knowledge, for example in workshops or seminars.
How to contain the threat posed by these bacteria is now being investigated by a multidisciplinary research team led by Eawag in the newly launched project "Legionella Control in Buildings" (LeCo). The project will last four years and was commissioned by the federal government.
More information on www.eawag.ch and under www.eawag.ch/leco
