Deadly Legionnaires’ Disease Outbreaks Persist in the U.S.

The most acute U.S. water contamination health risk defies control.

Under the right conditions, Legionella bacteria can multiply in building plumbing systems, including in faucets, showerheads, and cooling towers. Photo courtesy of Flickr/Creative Commons user Phil Roeder

By Brett Walton, Circle of Blue

Past investigations of Legionnaires’ disease have identified rooftop cooling towers, hospital plumbing, and ornamental fountains in restaurant lobbies as the source of outbreaks.

In New Hampshire last summer, though, none of those was the culprit in an outbreak of the deadly, pneumonia-like illness that is caused by inhaling water droplets contaminated with Legionella bacteria. This time, it was the hot tub.

State health officials traced the epidemic to the water system at the Sands Resort in Hampton, a popular Atlantic beach town. Inspectors found evidence of the bacteria in the hot tub, water heater, outdoor shower hose, and in the showerheads or sinks of three guest rooms. Between June and August, the peak period for the disease because of warmer temperatures, 18 people fell ill. One person died.

The Sands Resort wasn’t the only Legionnaires’ episode last summer.

An outbreak in New York City in July sent 25 people to the hospital and killed one. The source of the disease cluster was traced to a cooling tower at the Sugar Hill Project, a four-year-old apartment complex in the Lower Washington Heights neighborhood.

In September, an outbreak in Sioux Falls, South Dakota, hospitalized 15 people and killed one.

The three big disease clusters and thousands of individual cases are part of a surge in Legionnaires’ disease in the United States that distresses water and public health authorities. The rate of Legionnaires’ cases reported to the U.S. Centers for Disease Control and Prevention has increased four and a half times since 2000. Through September 29, local and state health agencies reported 5,520 Legionnaires’ cases this year to the CDC, a tally comparable to 2017, when 5,641 cases were counted in the same time period.

“The most significant waterborne, public health disease risk is Legionella as far as I’m concerned,” Joseph Cotruvo told Circle of Blue. Cotruvo is a former director of the U.S. Environmental Protection Agency drinking water standards division.

Cotruvo’s alarm stems from the acute risk of death. Chemical contaminants such as PFAS and nitrate are linked to cancers and other chronic diseases that develop after years or decades of exposure. Cryptosporidium, a parasite that causes severe diarrhea, is occasionally the source of a deadly outbreak. But Legionnaires’ disease, though not contagious, is the most worrisome waterborne illness in the U.S. because of its immediate devastating consequences.

The CDC only recently began tracking Legionella deaths. Based on data from 2011 to 2013, the agency estimates that the death rate is one in 10 overall and one in four when the disease is transmitted at a healthcare facility, where the patient already likely to be weakened. But those data came from only 10 states and selected counties that represented 36 million people. Comprehensive national data on death rates from 2014 and 2015 will be released at the end of the month, according to Kristen Nordlund, a CDC spokeswoman.

Knowledge and Prevention Are Lacking

Much is still a mystery about the spread and prevention of a disease that was first identified more than four decades ago, after 221 men were sickened and 34 killed during an American Legion convention in 1976 at Philadelphia’s Bellevue Stratford Hotel.

Legionella bacteria live in rivers and lakes, where they rarely sicken humans, but once inside plumbing systems they multiply and can be deadly. The bacteria flourish in warm, stagnant water found in cooling towers, faucets, showerheads, and other nooks and crannies in the pipe networks of hospitals, hotels, high-rise apartments, and nursing homes. Showers and faucets are the most common sources of outbreaks in buildings, according to a CDC analysis.

Why the rate of infection continues to increase is a matter of debate. One potential cause is older water pipes that could harbor bacteria. Those bacteria can enter the system when pipes break or be dislodged from slimes inside the pipe during construction. The bacteria can also grow when disinfectant or pH levels change, as happened in 2014 and 2015 in Flint, Michigan, where at least a dozen people died from the disease. Another factor is an aging population that is taking more medications that weaken immune systems. (Legionnaires’ is most harmful for people over age 50 and smokers.)

Yet another influence could be energy and water conservation practices. Turning down a water heater can bring the temperature into a range that is favorable for Legionella growth. Lower flows allow water to sit longer in pipes. The increase might also be attributable to better diagnostic tests and more observant doctors taught to look for Legionella. Detailed studies at hospitals in Chicago and Nashville of patients admitted for pneumonia suggest that there are more Legionnaires’ cases than are diagnosed. Some, or all of these factors are probably at play, says Laura Cooley, an epidemiologist on the CDC’s Legionella team.

Existing policies that work at cross purposes can be a hindrance. For instance, Cotruvo noted that a building that adds a disinfection system to kill bacteria could result in that buildings being classified as a regulated water system under the Safe Drinking Water Act. (The act applies to water treatment systems and the distribution network but does not regulate water quality in buildings.) That would mean additional water testing and reporting requirements that could be a financial burden, Cotruvo said.

“My concern is that it is a disincentive for facilities to put in additional treatment of water,” Cotruvo said. States are largely in charge of determining what rules to apply and their interpretations vary widely, he said.

Jasen Kunz from the CDC’s National Center for Environmental Health says that a strategy to control Legionnaires’ outbreaks requires three fronts: laboratory analysis to identify the disease, epidemiology to track the spread, and knowledge of environmental factors that contribute to bacteria growth.

Several industry associations and government agencies have developed standards in the last three years to guide building managers. In 2017, the Centers for Medicare and Medicaid Services, an agency within the U.S. Department of Health and Human Services, ordered healthcare facilities that accept Medicare to adopt measures to reduce the risk of Legionella.

With more vigilance, most outbreaks in buildings can be avoided, Kunz said. Awareness of preventative measures is low, but growing.

“Developing these evidence-based environmental prevention practices will ultimately equal a reduction in disease,” Kunz said at a conference in February. “However, Legionnaires’ disease experience is inadequate or completely lacking in most of the United States.”

Those uncertainties and inadequacies prompted the National Academies of Sciences, Engineering, and Medicine to investigate. A 13-member expert panel began an 18-month inquiry in February into policies for preventing the spread of Legionella in building plumbing. The panel will also assess why some of the dozens of Legionella strains are more virulent and what contributes to their growth in plumbing systems.

The panel’s next meeting on October 22 in Washington, D.C. is open to the public. It will also be webcast.

Brett Walton

Brett writes about agriculture, energy, infrastructure, and the politics and economics of water in the United States. He also writes the Federal Water Tap, Circle of Blue’s weekly digest of U.S. government water news. He is the winner of two Society of Environmental Journalists reporting awards, one of the top honors in American environmental journalism: first place for explanatory reporting for a series on septic system pollution in the United States(2016) and third place for beat reporting in a small market (2014). He received the Sierra Club’s Distinguished Service Award in 2018. Brett lives in Seattle, where he hikes the mountains and bakes pies. Contact Brett Walton