Every year, 52,000 to 70,000 Americans are afflicted by Legionnaires’ disease, a pneumonia caused by certain Legionella species. This is the conclusion of a research committee of the National Academy of Sciences, Engineering and Medicine, of which KWR Legionella expert, Paul van der Wielen, was also a member. The committee was set up after an increased incidence of the disease was observed between 2012 and 2017. The committee’s report now recommends measures that are very similar to the Legionella management measures that are already applied to buildings, drinking water installations and cooling towers in the Netherlands. One point of concern is that the widely used urine antigen test does not detect all types of Legionella infections.
The Legionella research committee
An expert committee of the prestigious National Academy of Sciences, Engineering and Medicine in the United States today published a report after almost two years of research, in which KWR’s Legionella expert, Paul van der Wielen, also participated. Here are some of the highlights:
- The report estimates that 52,000 to 70,000 people are afflicted every year by Legionnaires’ disease. This is ten times higher than the reported incidence.
- When water contains more than 5 x 104 Colony Forming Units of Legionella per litre, this is cause for serious public health concern, and actions need to be taken to reduce these numbers in the water system.
- The committee recommends that hot-water heater temperatures in all types of buildings be kept above 60°C, and the hot-water temperatures to distal points (far from the heaters) in the drinking water installation not be allowed to drop below 55°C.
- The committee recommends mandatory monitoring for Legionella in public buildings.
- The committee also wants to see mandatory Legionella management plans for all public buildings, including hotels, businesses, schools, apartments and government buildings.
Cooling towers need to be registered and monitored.
- And a new design for cooling towers is required to improve Legionella control.
Impetus: increased incidence of Legionnaires’ in US
The expert committee was set up in 2017, when it became clear that the incidence of Legionnaires’ in the United States had increased sharply between 2012 and 2017: Legionnaires’ disease afflicts more people in the US than all other waterborne diseases, while the country’s Safe Drinking Water Act has no controlling effect on Legionella.
KWR expertise used
The committee’s mission was to establish an overview of the current scientific knowledge regarding Legionella, and to draw on that knowledge to develop recommendations for Legionella management in the US. The committee comprised 12 American and Canadian experts, together with KWR Legionella expert, Paul van der Wielen, the only non-North American member; Prof. Joan Rose (Michigan State University and KWR Honorary Fellow) chaired the committee. Van der Wielen contributed his expertise primarily in the area of microbial ecology, Legionella sources and the legal and regulatory frameworks in European countries. KWR has provided advice regarding Legionella in the US on other occasions, including in Flint.
Comparison with the Dutch situation
The committee’s conclusions are of course aimed at the US. In Europe, by comparison, several measures have already been taken. For instance, Legionella threshold limits have already been established here for drinking water and cooling towers. Moreover, the temperature management now being recommended in the US is already in force here, as is the obligation to have a management plan and to monitor Legionella in priority buildings. The US recommendations concerning the cooling towers however go further than today’s Dutch policy: here, only cooling towers put into service after 1 January 2010 need to be registered.
Limited reported incidence of the disease
The American study also showed that the incidence of Legionnaires’ disease is much higher than the reported cases. The reason for this is that the most frequently used diagnostic test (urine antigen test) only detects L. pneumophila serogroup 1, so that cases with L. pneumophila serogroup 2-14 are often missed. In addition, the test is only conducted in hospitals, so that only patients with serious symptoms are tested. This aspect is also relevant in Europe where the same test is used, so that here the true of Legionnaires’ Disease incidence is much higher than the reported incidence.
The complete report can be found on the National Academy of Sciences, Engineering and Medicine website, where it can be downloaded. The page also offers a link to a short version of the report and the possibility of watching the webinar on the report’s presentation.