What’s happening with Legionnaires’ disease in Michigan

Legionnaires’ disease has been identified as a potential cause of death for two residents of a retirement community in Dearborn
General Motors has found the pneumonia-causing bacteria in one of its buildings in Warren, prompting its temporary closure
Researchers say the airborne disease mostly affects those with weakened immune systems with poor water system maintenance a likely driver of infection

Two deaths at a Dearborn retirement village and the closure of a General Motors engineering center have raised fresh concerns about Legionnaires’ disease in Michigan.

Legionella, the bacteria that causes the sometimes-deadly pneumonia and a flu-like illness called Pontiac fever, grows in human-made water systems. It’s been reported at several sites in Michigan this year, including an engineering facility at the GM Technical Center in Warren, which remains closed after two employees tested positive for Legionnaires’ disease earlier this month.

“We can confirm that water sampling at the Tech Center detected the presence of Legionella,” said Andrew Cox, director of Macomb County Health and Community Services, in a statement. “GM has been proactive in their investigation and response. There have been no additional cases.”

The Michigan Department of Health and Human Services has confirmed 34 cases of legionellosis — which can be either Legionnaires’ disease or Pontiac fever — in the last four weeks.

Cases included two fatalities over the summer at the Allegria Village retirement community, with health officials suspecting Legionnaires’ as the culprit after confirming the presence of the Legionella bacteria on site.

“MDHHS has been supporting Wayne and Macomb county health department legionella investigations by providing epidemiology and industrial hygiene support,” said Michigan health department spokesperson Lynn Suttfin in an email.

While Legionella is regularly found in the state, the US Centers for Disease Control and Prevention has noted a steady increase of Legionnaires’ disease nationally since the early 2000s.

What is Legionnaires’ disease?

Legionnaires’ disease, the most common form of illness caused by the Legionella bacteria, is a type of “severe pneumonia,” according to the CDC.

The lung infection can develop within two weeks of exposure to the bacteria, causing shortness of breath, headaches, fevers and muscle aches, sometimes with fatal results.

Related:

The disease got its name following a 1976 outbreak that occurred during the gathering of American Legion veterans at a convention in Philadelphia. The cluster of pneumonia cases affected at least 221 individuals and caused 29 deaths.

Legionella bacteria is also associated with Pontiac fever, a milder condition that causes flu-like symptoms without pneumonia. The illness was first identified in Pontiac, where at least 144 people contracted the fever in 1968, most of whom were employed by the Oakland County health department.

How does it spread?

Legionnaires’ disease spreads through bacteria-laden water droplets that float in the air and are then breathed in.

Legionella bacteria thrive in warm water settings and can exist in nature without posing a threat to humans. However, its increased prevalence in the US is associated with building water systems and infrastructure.

A graph of Legionnaires' disease in the United States from 2000 to 2022. — Legionnaires’ disease incidence has been increasing since 2000. (Courtesy of US Centers for Disease Control and Prevention)

Air conditioning units and their cooling towers, potable water used in showers, hot tubs and decorative fountains have been cited as sources for contamination.

In Flint, where a 2014-2015 Legionnaires’ outbreak coincided with the city’s water crisis, researchers have pointed to a drop in chlorine levels within the municipal water supply as a likely source of kicking off one of the nations’s largest outbreak of legionellosis. At least 90 Genesee County residents contracted the disease.

“When the city started treating the water rather than purchasing it from Detroit, they did not add the anticorrosive that is standard practice,” Michele Swanson, a professor of microbiology and immunology at the University of Michigan Medical School who has studied Legionella for decades.

“When lead and other heavy metals leach off of corroding pipes, they interact, bind to the chlorine and basically take it out of the equation.”

Swanson said Legionnaires’ also occurs seasonally, with warmer weather during the summer contributing to bacteria growth.

Others have pointed to climate change as a potential driver for increased infections. Increased surveillance and awareness may also contribute to more cases being reported.

Who is most likely to get it?

Those with a weakened immune system.

Stephanie Shames, an infectious disease researcher at Michigan State University who studies how Legionella grows within the body, said the increased spread of Legionnaires’ disease seen nationally can be partially tied to the aging population.

“Anyone who’s on an immunosuppressive therapy or even chemotherapy are going to be more susceptible to disease,” she said.

Most healthy people do not get sick after exposure, Shames said, but can still develop Pontiac fever. The condition is often underdiagnosed because people may not see a doctor for the illness.

The CDC also lists current and former smokers and those with chronic lung disease as more at risk of getting sick after being exposed to Legionella.

Is it deadly?

It can be.

A cluster of Legionnaires’ disease cases in Harlem this summer was tied to seven deaths, according to the New York City Health Department. 90 people were hospitalized.

According to NYC officials, at least 90% of the people with Legionnaires’ disease had a known risk factor for severe disease.

At least a dozen people died from Legionnaires’ during the Flint water crisis.

How is it treated?

Like other forms of bacterial pneumonia, Legionnaires’ disease can be “well controlled” by antibiotics if caught early, according to Shames.

“There’s a correlation between the time to diagnosis and severity of the disease,” she said. “If you wait too long to administer antibiotics, even if you can get rid of the infection, sometimes you’ll have permanent lung damage.”

Those patients, Shames said, may need breathing treatments for the rest of their lives.

Pontiac fever resolves on its own, and those infected are usually instructed to rest.

Can it be prevented?

The best treatment for Legionnaires’ disease may exist outside the human body.

Legionnaires’ disease outbreaks are “100% preventable if the freshwater systems are maintained properly,” Shames said.

A committee of the National Academies of Sciences, Engineering, and Medicine (NASEM), which estimates Legionnaires’ affects 52,000 to 70,000 each year, has recommended better management and monitoring of water systems as a way to drive down Legionella.

“We don’t have a public policy that requires building management teams to regularly test for Legionella. So that’s a problem,” said Swanson, who served on the committee. She adds that hot and cold water should be kept separate from one another in plumbing to avoid bacteria growth.

“Buildings … especially ones that have high risk residents, like the long term care facilities, they should be testing their water regularly for levels of the decontaminant, typically some kind of chlorine, to make sure they’re adequate.”