Legionella bacteria. Image: Wikimedia Commons

Why Are People Still Dying from Legionnaires' Disease?

We actually know a lot about how the disease spreads, so why are people still dying?

Aug 6 2015, 12:00pm

Legionella bacteria. Image: Wikimedia Commons

With its rather innocuous name, Legionnaires' Disease can easily be underestimated. But the bacteria-borne infection can be devastating, leaving some victims with lifelong complications—even amputations—and has a mortality rate of up to 30 percent.

And while the average person might be baffled by the little-talked-about but deadly illness, researchers who have studied it for decades have few questions about Legionnaires' Disease, how it spreads, and how to prevent it. We've had this knowledge for years, so why are people still dying?

Right now, a community in the south Bronx in New York City is in the throes of a deadly outbreak of Legionnaires' Disease. Since July 10, there have been 86 confirmed cases of the disease. Seven people have died.

This week, New York Mayor Bill de Blasio said officials identified Legionella—the bacteria that causes the disease—in five water cooling towers at apartment complexes in the Bronx. Cooling towers hold the water used to heat, cool, and circulate air in large buildings, though officials aren't yet clear on how many of the towers contributed to this breakout.

The number of cases being reported is slowing, but with a mortality rate of 8 percent so far, it's not an outbreak to be ignored.

"We know an awful lot about the organism of the disease, where to find it, and how to stop it," explained Janet Stout, the director of the Special Pathogens Lab and an environmental engineering professor at the University of Pittsburgh. Stout has specialized in researching Legionella for more than 30 years and says we should be able to prevent these kinds of outbreaks with better monitoring.

Legionnaires' disease got its name after a deadly outbreak in 1976 during a convention in Philadelphia for members of the American Legion. Since naming the disease, researchers have been able to identify the related bacteria and understand a great deal about the causes, treatment, and possible prevention of the disease.

"It's not as rare as people think."

There are actually 58 members of the Legionella family of bacteria, Stout told me, only half of which can cause the illness. Legionella bacteria are found naturally in rivers and ponds, but usually in small, harmless numbers. The trouble comes when a small number of Legionella bacteria travel through our water treatment systems—the bacteria isn't very susceptible to the chemicals we use to treat our water, Stout said—and winds up in a cozy environment where it can start a family.

"It finds conditions that it likes or needs to grow: warm temperatures, other sources of food like the dirt and sediment normally found in pipes and cooling towers, and other microbes and bacteria that help Legionella to grow and multiply," Stout said over the phone. "All of those conditions are present in those warm water systems."

The disease isn't spread from person to person. Once a batch of Legionella starts to colonize an environment (like a cooling tower or a hot tub) it can grow to dangerous numbers. If the bacteria is then vaporized (like through air conditioning or the steam from said hot tub) and inhaled, or directly ingested through drinking contaminated water, it can get into the lungs and cause the nasty, pneumonia-like infection, Stout explained.

If the bacteria gets into the lungs, you still probably won't get sick. Stout told me even in an outbreak situation, only about 2 to 5 percent of people exposed will actually contract the disease. It all depends on your underlying health condition (so older people, smokers, or those with weakened immune systems are more vulnerable) and how much bacteria gets in.

But if you do get sick, Legionnaires' can be devastating and even deadly. Because early symptoms are flu-like, it can go undiagnosed, and other kinds of common antibiotics that a doctor might prescribe aren't effective, Stout said. There are effective antibiotics that can knock out Legionnaires' Disease if caught early, but for many people, especially early in a breakout, it's just not considered as a possibility until it's too late.

Once Legionella gets into the lungs, it wreaks havoc due to its natural ability to wriggle its way inside other cells, like the pulmonary macrophage.

"I sort of describe the macrophage as Pac-Man: it goes through the lung, eats up stuff that comes down into the lung, and then breaks it up and destroys it," Stout said. "Legionella has a unique ability to circumvent that process. Instead of being killed, it multiplies inside those cells that are there to defend us and then spills out into the lung and causes inflammation. Then it travels through the bloodstream through the kidneys and elsewhere."

The good news is we do know ways to prevent it. Studies have shown regularly testing of at-risk water systems (like hot tubs, fountains, hospital water systems, and cooling towers) for Legionella can help catch an outbreak before it starts. But turning this knowledge into regulation has been a lagging process. In fact, Legionella-related illnesses are on the rise in the US, though we've known good ways to prevent it for decades.

Matt Freije, who owns a consulting firm that helps building operators inspect for and prevent the growth of Legionella, thinks that may be because of a perception that the disease is quite rare.

"It's not as rare as people think," Freije told me over the phone, pointing out that the Centers for Disease Control and Prevention estimates between 8,000 and 18,000 people in the US are hospitalized from Legionnaires' disease every year. But because a community is more likely to see just one or two cases at a time, rather than a headline-grabbing outbreak of dozens of people, they go largely unnoticed, Freije said.

"To some extent, it's just been a lack of awareness," Freije told me. He also said the costs associated with consistent monitoring may have deterred some building operators, and that there has been some confusion over how effective monitoring is, since you can have some Legionella in a cooling tower without any risk of disease.

But there are shifts happening. Earlier this year, the American Society of Heating, Refrigerating, and Air-Conditioning Engineers published its first-ever guidelines for mitigating the risk of Legionella in building water systems. In New York, Mayor de Blasio has also pledged to beef up regulations for inspecting cooling towers in the city, saying the city hadn't acted sooner because it wasn't clear that cooling towers were linked to the spread of the disease.

In the meantime, if you live in the south Bronx and are experiencing flu-like symptoms, officials are recommending you go to the doctor immediately.