Multiple sources of Genesee County Legionella Outbreak in 2014-2015

Legionnaires’ disease is a severe kind of pneumonia (lung infection) caused by the bacteria Legionella pneumophila. These bacteria can grow in warm water systems and become airborne in showers, cooling towers, and air conditioning systems. People typically catch it by breathing in air with tiny water droplets (called aerosols) that contain the Legionnaires’ disease bacteria.

In order to prevent new outbreaks in Genesee County – and elsewhere – it is vital to understand how people got exposed to Legionnaires’ disease bacteria. If we know how people got exposed it helps to understand what caused the outbreak.

Independent Legionnaires’ disease research

The research team travelled to Lansing and Flint and studied the information that was available about the Legionnaires’ disease epidemic in Genesee County in 2014 and 2015. The team evaluated medical records, disease and death statistics, Census data, address data, water connection and use data, hospital data, Flint water data, geographical data, and weather data.

To ensure an independent research practice we did not rely on what others had collected or analysed but went back to the most primary data available. Gertjan Medema: “We basically positioned ourselves as first on the scene and took the research steps that epidemiologists take when confronted with an outbreak. We reviewed information about each of the 86 residents from Genesee County who was diagnosed with Legionnaires’ Disease in 2014-2015 and used multiple reviewers per file (each file was reviewed twice). We were able to find out when each person got Legionnaires’ disease, and how each person might have been exposed to the Legionnaires’ disease bacteria.”

Three sources associated with the outbreak of Legionnaires’ disease

An outbreak of Legionnaires’ disease occurred in 2014-2015 among people who lived in Genesee County. A total of 86 residents of Genesee County developed Legionnaires’ disease. Most of the people who developed Legionnaires’ were age 65 or older and had a chronic health condition.

We found strong evidence (CDC class I) for exposure to a Flint hospital in 2014 and 2015, and weaker evidence (

) for exposure to City of Flint water at home or living in the proximity of a specific cluster of cooling towers in Flint.

Flint hospital

Nearly half (42 of 86 persons) had been in this hospital before they got sick with Legionnaires’ disease. Most of these 42 people had been hospitalized, but some of them were visitors or outpatients. We have strong evidence that people in Genesee County got sick with Legionnaires’ disease because of their contact with this hospital:

• More cases had contact with this hospital than would be expected if this was coincidence;
• Legionella pneumophila was present in the plumbing system of the hospital, during the outbreak period and, in some samples tested, in high concentrations;
• Using advanced genome testing, Legionella pneumophila strains from the hospital’s plumbing system were highly similar to strains that were isolated from people who had been in the hospital with Legionnaires’ disease;
• Right after the hospital implemented effective Legionella control with superheating/ chlorination and monochloramine no new cases of Legionnaires’ disease occurred among people who had been at this hospital.

City of Flint water at home

Of the 86 people who came down with Legionnaires’ disease, 29 had City of Flint water service at their homes during the outbreak. Some of these people had also been at the Flint Hospital before they came down with Legionnaires’ disease. We observed that residents on City of Flint water had a higher risk of acquiring Legionnaires’ disease than Genesee County residents that were not served by City of Flint water in 2014. This was not the case in 2015.

In a study by scientists from Virginia Tech in August 2015, Legionella pneumophila was not detected in 31 small buildings (including homes) in the City of Flint. This makes us less confident about the residence on City of Flint drinking water being a source of the observed Legionnaires’ disease cases than we are about the hospital being a source.

Living close to a specific cluster of cooling towers

We observed that people living closer to a cluster of cooling towers in Flint had a higher risk of acquiring Legionnaires’ disease in 2014, but not in 2015. Of the 86 people, only a small number of people may have gotten exposed to Legionella pneumophila at their homes through aerosols coming from any of a cluster of five cooling towers. Some of these people had also been at the hospital before they came down with Legionnaires’ disease. Again this makes us less confident about cooling towers being a source of the observed Legionnaires’ disease cases than we are about the Flint hospital being a source.

How to prevent Legionnaires’ disease epidemic?

There are multiple lessons to be learned from the Legionella outbreak in Genesee County. Gertjan Medema: “Our research has focussed on what happened during the epidemic in 2014 and 2015. Even though that will not change what happened, we are obliged to learn from outbreaks: what happened and what lessons do we extract to improve Legionella prevention and response Therefore we included recommendations we drew from our study on how to better prevent such an epidemic and on how to improve the response in case a Legionnaires’ disease epidemic is detected.” The recommendations are attached to this press release.

Legionella management

An expert committee of the National Academy of Sciences, Engineering and Medicine in the United States published a report on management of Legionella in water systems. The committee comprised twelve American and Canadian experts, together with KWR expert Paul van der Wielen, the only non-North American member. Van der Wielen contributed his expertise primarily in the area of microbial ecology, Legionella sources and the legal and regulatory frameworks in European countries. The report concludes that stronger guidance and action is needed to combat the growing number of Legionella infections and outbreaks in the US. The committee’s report 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 and some other European countries. The report can be downloaded from the National Academy of Sciences, Engineering and Medicine website.

About the study

Our study was financed by the State of Michigan. The State defined the objective of the study “to investigate the cause of the Legionnaires’ disease outbreak, in order to learn from this outbreak and prevent future outbreaks”. As a scientific institute, independence and objectivity are KWR’s core values. To ensure our independence we agreed beforehand that, whatever the results, KWR would publish the results of our investigations in a peer-reviewed scientific journal. We also agreed that we would adhere to the international standards of scientific integrity and quality and that our study design, results and conclusions would be reviewed by an independent panel of experts.

Link to the Environmental Health Perspectives article

Information for the press

• KWR Water Research Institute (Nieuwegein, The Netherlands)
• Press Officer: Hans Ruijgers, e-mail
• Lead researcher: prof. Gertjan Medema PhD, e-mail , profile page https://www.kwrwater.nl/en/experts-expertises/experts/gertjan-medema/

Epi curves

Epidemic curve of the outbreak of Legionnaires’ disease in Genesee County in 2014 and 2015. Each person that contracted Legionnaires’ disease is depicted as a block in the curve. The top curve shows how the persons in Genesee County contracted Legionnaires’ disease over time. The middle curve shows the exposure to the Flint hospital and the timing of the Legionella interventions in the hospital’s water system. The bottom curve shows the exposure to City of Flint water at the home and the timing of the switch of the drinking water source to Flint river water and back to Detroit water.

Epidemic curve of the outbreak of Legionnaires’ disease in Genesee County in 2014 and 2015. Each person that contracted Legionnaires’ disease is depicted as a block in the curve. The top curve shows how the persons in Genesee County contracted Legionnaires’ disease over time. The middle curve shows the exposure to the Flint hospital and the timing of the Legionella interventions in the hospital’s water system. The bottom curve shows the exposure to City of Flint water at the home and the timing of the switch of the drinking water source to Flint river water and back to Detroit water.

Epidemic curve of the outbreak of Legionnaires’ disease in Genesee County in 2014 and 2015. Each person that contracted Legionnaires’ disease is depicted as a block in the curve. The top curve shows how the persons in Genesee County contracted Legionnaires’ disease over time. The middle curve shows the exposure to the Flint hospital and the timing of the Legionella interventions in the hospital’s water system. The bottom curve shows the exposure to City of Flint water at the home and the timing of the switch of the drinking water source to Flint river water and back to Detroit water.

How to prevent a Legionnaires’ disease epidemic?

There are multiple lessons to be learned from the Legionella outbreak in Genesee County.

Hospital

Hospitals are well-known sources of Legionella outbreaks, because they combine 1) a large building with a complex warm (and cold) water system where Legionella may grow, and 2) people that stay in this building being generally older and having weakened immune systems or chronic disease, and therefore being more likely to develop Legionnaires’ disease than younger, healthier people.

We recommend
That all hospitals and large healthcare facilities follow the existing guidelines on how to manage Legionella in water systems in complex large buildings.

Additionally, if a person who has been in a hospital (or long-term care facility) develops Legionnaires’ disease, close coordination with local public health officials should occur promptly.

Implementation of effective prevention of Legionnaires’ disease requires additional coordination between all levels of government in Michigan, and also requires expanded capacity at the state and local health department levels.

Water utilities

We recommend
That public water utilities in Michigan supply water that contains sufficient disinfection residual and is low in iron and nutrients for bacterial growth to help control Legionella in water

.

Cooling towers

Cooling towers are also well-known sources of Legionella outbreaks.

We recommend
The development and implementation of cooling tower regulations in Michigan, similar to those used by New York City and New York State.

Homeowners

We are aware of no evidence that homeowners/residents contributed to the outbreak. In other settings, home humidifiers and hot tubs have led to outbreaks of Legionnaires’ disease. However, homeowners/renters – particularly those with chronic lung disease, chronic kidney disease, and other chronic health problems – can take actions that might reduce the risk of being exposed to Legionella.

We recommend
That water utilities and housing associations in Michigan proactively issue advice to homeowners/renters about Legionnaires’ disease prevention, similar to advice given in the Netherlands and the recommendations of MDHHS for residents.

How to act when a Legionnaires’ disease epidemic is detected?

When a Legionnaires’ disease outbreak is suspected,

Ensure
Rapid follow-up of people who acquired Legionnaires’ disease to identify, inspect and sample potential sources and bring the outbreak source(s) under control to prevent new disease cases. This requires effective collaboration between County, State and Federal health agencies during non-outbreak times, to be able to quickly act upon a suspected outbreak.

We recommend
That when a person who has been in a hospital (or long-term care facility) develops Legionnaires’ disease, close coordination with local public health officials occurs promptly.

To timely sample suspected environmental sources in an outbreak and analyse for Legionella.

In our research, the source attribution was also hampered by the low number of isolates from people who acquired Legionnaires’ disease. That is not uncommon in outbreak investigations, but especially in a multisource/complex outbreak and at the early stages of the outbreak the availability of many isolates might help identify common source(s).

We recommend
Testing sputum samples from people with possible Legionnaires’ Disease so that isolates found to contain the bacteria can undergo “DNA fingerprinting” in support of the outbreak investigation.

When hospitals/large buildings are suspected as source of Legionnaires’ disease,

We recommend
Conducting a thorough and comprehensive inspection and sampling of the water system as soon as possible.

Including the hot and cold water system and other water systems (including ice machines). If Legionella pneumophila is detected in concentrations of >1000 cfu/L, evidence-based remedial actions should be taken promptly.

That hospitals and other healthcare institutions make sure they hire a consultant with demonstrated expertise in Legionella investigation and control, as specified in the CDC-guidance.

How to quickly identify hot cooling towers?

We recommend

Making a registry of wet cooling towers and communal and industrial wastewater treatment plants, and other outdoor aerosol-generating operations.

We have developed an approach to quickly identify potential hot cooling towers in our study based on the information about the location of the people with Legionnaires’ disease. This approach is now available and may be useful in future outbreak investigations.