Emerging Factors Impacting Legionnaire’s Disease: A Rising Concern

Posted on Behalf of  Corey Boles, Olivia Leleck

Posted on behalf of Corey Boles and Olivia Messina Leleck.

In the United States (U.S.) this year alone, over 20 outbreaks of Legionnaire’s disease have been reported, resulting in hundreds of illnesses and nearly 20 deaths (HC Info, 2019). Legionnaire’s disease is a form of pneumonia caused by inhaling droplets containing Legionella bacteria, which naturally occurs in freshwater environments (CDC, 2016). Legionella can become a human health concern when it grows and spreads in water systems such as cooling towers and large plumbing systems (i.e., those used in hospitals and hotels) because of improper water maintenance (CDC, 2016). This year’s largest outbreaks, for example, were linked to the cooling towers, hot water distribution systems, and hot tubs at hospitals, hotels, and a state fair (Aldridge, 2019Brumback, 2019Stankiewicz, 2019Wahlberg, 2018). The rate of reported cases of Legionnaires’ disease in the U.S. increased more than eight-fold in the past two decades. Cases are expected to continue to increase due to the aging population, rising global temperatures, and decaying plumbing infrastructures (e.g., aging pipes and water systems) (Cunha et al. 2016; Lee 2018; Rubin 2018; Weber, 2019).

In addition to individual factors such as age and smoking status, certain occupations may be at an increased risk of contracting Legionnaire’s disease (CDC, 2016). Individuals involved in water management for a building or set of buildings (e.g., plumbing, facilities management, and custodial staff), as well as property managers, general contractors, real estate agents, hotel staff, and medical professionals can become exposed to aerosolized Legionella from multiple areas along the water distribution system of a building (NIOSH, 2019). The risk of infection after occupational exposure can compound if the worker falls into another susceptible population (e.g., immunocompromised).

Environmental factors may also contribute to Legionella growth.  Increasing global temperature may contribute to increases in cases of Legionnaires’ disease, as community-acquired pneumonias becomes more common with rising temperature and humidity (Rubin 2018; Simmering et al., 2017).

As evidenced by this year’s outbreaks, factors such as aging infrastructure, poor water system maintenance, and building and water distribution design can also promote Legionella growth and aerosolization (Lee 2018; Snell & Sanders 2018; Rubin 2018; Simmering et al., 2017). These systems often have areas neglected or overlooked because of their complexity and building-specific design, which can lead to microbial growth, biofilm formation, and environmental exposure (CDC, 2016). Legionnaire’s outbreaks, for example, are often linked to cooling towers, hot water systems, and decorative fountains that commonly comprise a large portion of a building’s water distribution system (CDC, 2016). Monitoring water distribution systems can help reduce the likelihood of Legionella growth.

In addition to these factors, the National Academies of Sciences, Engineering, and Medicine (NASEM) recently stated that unintended consequences related to green buildings, such as lower hot-water temperatures in plumbing, likely contribute to the increasing incidence of Legionnaire’s disease (NASEM, 2019). Authors of two different studies also reported that there were higher colonization rates of Legionella and Pseudomonas aeruginosa in conventional plumbing systems fitted with electronic-eye or hands-free metered faucets when compared to conventional faucets (Yapicioglu et al., 2012; Sydnor et al., 2012). While the intent of green building design, construction, or operation is meant to be environmentally responsible and resource-efficient, this approach may inadvertently create a public health concern by creating ideal conditions for Legionella growth. The NASEM recommended actions to prevent growth of Legionella in water distribution systems, such as not allowing low-flow fixtures in hospitals, long-term care facilities, and other buildings with high-risk occupants (NASEM, 2019). They also recommended modifying criteria for certifying green buildings, energy-conserving features, and water conservation features to account for risk factors associated with the Legionella growth in building water systems (NASEM, 2019).

With so many different occupations, industrial sectors, and facilities at risk, healthcare facilities, nursing homes, hotels, and other public-facing industries especially need to understand strategies for preventing Legionnaire’s outbreaks. Several procedures can be implemented at the individual facility level to ensure that Legionella growth is controlled. Each multitenant facility should have a verified and validated water management plan, including a risk assessment of the building’s water distribution system. The CDC notes that most outbreaks can be traced back to buildings that had either missing or inadequate water management plans (CDC, 2016). In addition, validated and verified disinfection protocols and guidelines should be followed and monitored. Lastly, risk management and communication among not only the water management plan team, but also among all of the building tenants, is crucial for preventing the growth and spread of Legionella

CardnoChemRisk conducts microbial risk assessments at commercial and industrial facilities. Our diverse team of microbiologists, industrial hygienists, epidemiologists, and toxicologists conduct extensive exposure assessments associated with Legionella and provide control and prevention recommendations. To learn more about our capabilities, or if you have any questions regarding this topic, please contact Dr. Antony Jones.