Ray Hozalski and the Case of the Opportunistic Pathogens in Grand Rapids, Minnesota

In 2024, the City of Grand Rapids, Minnesota, saw a spike in Legionnaires’ Disease. As the Minnesota Department of Health (MDH) began to investigate and consider remedial options, who did they call? Ray Hozalski. 

Being of service is sometimes a result of being knowledgeable and prepared and ready to take action at that moment of need. Ray Hozalski is well prepared to support cities’ drinking water distribution systems through his expertise with water systems and opportunistic pathogens like Legionella pneumophila, the bacteria that causes Legionnaires’ disease. So, when Sandeep Burman, the head of the Drinking Water Protection Division at the MDH, contacted him, Hozalski was ready to be of service. 

The MDH tapped Hozalski to join a team of experts from the U.S. Environmental Protection Agency (USEPA), U.S. Centers for Disease Control (CDC), MDH, and consulting firms, to provide insight and advice on the worrying outbreak of Legionnaires’ Disease. 

Preparation

Hozalski began studying bacteria and water treatment processes in graduate school, an initiation that led to a long career of research to improve the quality of drinking water. Now Hozalski’s primary research interest concerns microorganisms in water, both their ability to cause disease in humans (i.e., waterborne pathogens) and their beneficial uses for water purification.  

One of his areas of specialization is the microbial communities that live on the inside of water pipes and other solid surfaces. Such communities, called biofilms, can work in service of clean water as in a treatment process called biofiltration, or they can adversely affect the quality of water at your home’s tap.

Hozalski’s goal has always been to enhance our understanding of the structure and function of biofilms in engineered water systems (e.g., filters, pipelines) and to use that understanding to develop or improve water treatment processes that use biofilms. 

Although Hozalski has been studying water systems for a long time, he can still be surprised. The situation in Grand Rapids presented some unique challenges.

Active Crisis

Grand Rapids was experiencing an active public health crisis. Between 2023-2024, Grand Rapids had a spike in reported cases of Legionnaires’ disease. Many people were hospitalized and two died. 

Legionnaires’ disease is a type of pneumonia. It was first identified in 1976 after an outbreak at a conference of the American Legion in Philadelphia. Infected individuals can experience a range of symptoms, including shortness of breath, fever, headaches, and respiratory and gastrointestinal problems. Healthy individuals who get infected may have mild flu-like symptoms that resolve on their own, those cases are referred to as Pontiac fever. But the more severe cases of Legionnaires’ disease primarily affect immune-compromised individuals. The disease is not spread person-to-person nor by drinking compromised water, but rather, by inhaling or aspirating contaminated water droplets into the lungs. Exposure can happen by breathing in tiny water droplets called aerosols emitted from showers, fountains, or other water sources that are contaminated with pathogenic Legionella. Exposure has also been associated with contaminated cooling systems for large buildings, as was the case in Philadelphia back in 1976. 

There is no vaccine for the disease. The problem has to be addressed through maintenance of the water distribution system and building cooling towers. Typically, Legionella pneumophila needs three things to grow: warm temperatures, carbon for food, and little or no disinfectant (chemicals added to kill bacteria and viruses) in the drinking water. Flushing, temperature control, and disinfection help control the disease. Regarding the situation in Grand Rapids, Hozalski said, “Solving a problem like this is pretty motivating, it is the ultimate goal of my research.” So, he dug in to help find a solution.

Opportunity within the Crisis

The Grand Rapids situation presented an opportunity for a natural full-scale experiment. Water distribution systems are complex with many variables: water source, location, temperature, disinfection method, and water storage differences, including the use of large storage towers, to name a few. It is difficult to compare systems with so many variables. 

A unique aspect of the Grand Rapids situation was that a Legionnaires’ disease outbreak was attributed to a system that obtained its water from groundwater. Groundwater sources are generally considered cleaner than surface water sources because the water is naturally filtered through layers of gravel and soil. Federal regulations do not require disinfection for water systems that use groundwater, as long as the drinking water regularly tests free of coliform bacteria—indicating that there is no contamination from fecal matter. Hence, the Grand Rapids water system was not using disinfection prior to or during the outbreak. The Grand Rapids site presented Hozalski and his team the chance to study an active system in a wide-scale crisis, to recommend a solution, and to assess the impact of the intervention. Hozalski was also able to leverage a large, existing research project to provide the data to help.

An Existing Research Study Provides Serendipity

Disinfection stifles pathogens that can harm humans, but adding disinfectants to drinking water can also carry risks by creating so-called disinfection byproducts that might also be harmful to human health. When he received the call from Grand Rapids, Hozalski was leading a large USEPA-sponsored project to study the complex interactions and tradeoffs involved when disinfecting drinking water. Hozalski’s study was looking at various disinfectants, the byproducts produced, and what concentrations led to the best results in terms of minimizing exposures to both opportunistic pathogens and disinfection byproducts. 

The research team working on the large USEPA project consisted of Hozalski, his CEGE colleague Timothy LaPara, and their students and post-doc at the University of Minnesota, along with professors Srijan Aggarwal from the University of Alaska Fairbanks, Carsten Prasse of Johns Hopkins University (Baltimore, Maryland), and John Sivey of Towson University (Towson, Maryland) and their staffs. That project was carefully planned: the researchers planned to gather data over six seasons, including twice in consecutive summer and fall seasons, where the warmer water favors the growth of Legionella pneumophila. The researchers gathered samples from 21 water treatment plants operated by 18 water utilities across the continental U.S. and Alaska. Samples from each site were gathered by utility personnel and half of the samples shipped to Maryland for analysis of disinfection byproducts at Towson University. The Minnesota team would analyze for Legionella pneumophila and other opportunistic pathogens. 

When he got the call from MDH, Hozalski was able to add the Grand Rapids system into his larger, ongoing research project. This proved to be helpful from a research perspective because of the unique aspects of the Grand Rapids situation, but also from a public health perspective because it enabled rapid high quality data to be collected to help the team of experts recommend potential solutions. 

Results from Grand Rapids

Because of the number of buildings around the city that tested positive for Legionella pneumophila in testing done by MDH, the City, and Hozalski’s team, it was determined that the source of the organism had to be the city water supply. Interestingly, despite the ongoing outbreak, Legionella pneumophila was not detected in the so-called “finished water” leaving the treatment facility nor was it detected in water samples collected from the city’s water mains. The next step was to analyze water from several buildings within the city. There the team often found high levels of Legionella pneumophila. It seemed the bacteria was growing in the plumbing within the buildings. Finding high concentrations of these bacteria at showers and sinks, while failing to detect Legionella pneumophila in the water entering the buildings suggested that the organism was either present intermittently in the city supply or at concentrations too low to be detected by the team’s methods.

It appeared that without disinfection the combination of sufficient nutrients in the water supply and plumbing in the homes and commercial buildings of Grand Rapids was creating an environment conducive to the growth of Legionella pneumophila. Water from premise plumbing, showers in particular, seemed to be making some people sick.

The Chosen Solution 

One option was to “spot treat” the problem, to flush and disinfect specific buildings found to have high levels of Legionella pneumophila. A few buildings did just that as a quick fix. However, disinfection at the individual building-level would be difficult to implement and monitor, and the results would likely be inconsistent, perhaps resulting in continually chasing after contamination events. After lengthy deliberation among the team of experts, a centralized action involving disinfection at the water treatment plant was recommended, that would allow the disinfectant to spread and protect the entire city. Hozalski concurred. The City and the researchers determined that the source of the problem, the City water system, could also be the key to the solution. 

Because of his extensive research background and outstanding team of colleagues and students, Hozalski was able to offer insight into the occurrence of Legionella pneumophila in the system and remedial alternative. More careful consideration and testing by a consulting firm led the City to select the specific disinfectant to be used. In June of 2024, the City of Grand Rapids began dosing the disinfectant chloramine into the city’s drinking water distribution system. Hozalski’s USEPA Team was standing by to do the analysis.

The Results

It has been a year since disinfection with chloramines was implemented in Grand Rapids, and no new cases of Legionnaires’ disease have been reported. The intervention proved to be speedy and successful. This was very good news for the residents of Grand Rapids and an exciting scientific study for the Hozalski research team. 

Hozalski previously served on the U.S. EPA Science Advisory Board Drinking Water Committee. He was appointed to the U.S. EPA Science Advisory Board Microbial and Disinfection Byproduct (MDBP) Revision Review Panel for 2025. The MDBP Revision Review Panel planned to review the draft analysis to support the EPA’s revisions of the MDBP National Primary Drinking Water rules.