By: Heather Williams

Legionnaires’ disease.  How often does it really occur in the United States?  The answer might surprise you.  With cases of Legionnaires’ disease on the rise, it might just be something to be on the lookout for.  According to the CDC, Legionnaires’ cases have increased by 450% in the last 15 years bases on a study investigating data from 2000 to 2015.  About 6,000 cases of Legionnaires’ disease was reported in 2015.  Though the CDC expected that is very underestimated because the disease is often underdiagnosed.  This may not sound like much, but with a one in 10 mortality rate, it is quite concerning.  The water crisis in Flint, Michigan has contributed to the increase in cases.

What is Legionnaires’?

The bacteria Legionella causes Legionnaires’ disease or Pontiac fever.  This disease is also known as legionellosis.  The namesake of the bacterium comes from an outbreak that occurred in 1976 where many people who attended a Philadelphia convention of the American Legion were sickened with pneumonia.

How Do You Get Legionnaires’?

Legionnaires’ is contracted when a person breathes in small droplets of water from the air that contains the harmful bacteria Legionella.  While it is not a very common mode of transmission, Legionnaires’ disease can be contracted by aspiration of contaminated drinking water.  This happens when water “goes down the wrong pipe,” where a person is drinking and the water enters the trachea or windpipe instead of going down the throat into the digestive tract.  Those with existing swallowing difficulties are more likely to be at risk for this method of transmission.  This disease is generally not spread from person to person except for very rare circumstances.

The bacteria are more commonly found in nature in fresh water environments in places like lakes and streams.  Most cases occur when Legionella finds its way into human-made water systems such as building plumbing.  These are areas such as hot tubs, hot water tanks and heaters, larger plumbing systems, and decorative fountains.  Legionella is also a concern for air-conditioning system cooling towers found in large buildings.  Air-conditioning units in homes and in cars do not use water to cool the air, so they do not have the same risk factors for Legionella growth that large buildings have.

Hot tubs in particular are at a very high risk for being contaminated with Legionella bacteria.  This bacterium grows best in warm water, such as that used in hot tubs.  Unfortunately, this warm environment makes it hard to keep disinfectants, such as chlorine, at high enough levels to kill harmful bacteria like Legionella.  For this reason, chemical levels in hot tubs should be monitored regularly and should be cleaned as recommended by the manufacturer.


Symptoms of Legionnaires’ disease are like those of pneumonia.  Symptoms include headache, fever, chills, ataxia (lack of muscle control for voluntary movements), tiredness, cough, shortness of breath, muscle aches, nausea, diarrhea, and vomiting.  Symptoms appear between 2 to 10 days after exposure.  Once infected, the patient may develop a persistent cough, chest pains, and sometimes additional breathing problems.

You should contact your health care provider and/or the local health department if you believe you may have been exposed to Legionella and you have symptoms such as fever, cough, chills, or muscle aches.

Legionnaires’ disease is treated with antibiotics.  In severe situations, life-threatening complications may occur, such as lung and kidney failure.  Other complications include septic shock caused by a subsequent blood infection that may cause a sudden and unsafe drop in blood pressure.

Who is at Risk of Legionnaires’ Disease?

While anyone can be exposed to the Legionella bacterium, most health people show no symptoms or recover quickly.  For some, Legionnaires’ is a greater concern.  People who are 50 years or older have a higher risk of infection along with those with certain medical issues.  People with chronic lung disease such as obstructive pulmonary disease or emphysema are at a higher risk.  Those with a weak immune system or take drugs that weaken the immune system (such as chemotherapy and drugs taken after a transplant operation) are also at a higher risk.  People with cancer, underlying illness such diabetes, kidney failure and liver failure are in this high-risk category as well.

Flint, Michigan

The Flint, Michigan water supply has been a recent concern and is the driving location responsible for many of the Legionnaires’ disease cases.  Between 2014 and 2015 nearly 100 cases of Legionnaires’ have been reported as well as 12 deaths.  While it is possible that the increase in cases may be due to better diagnostic tests and better identification and monitoring at hospitals (particularly in areas at a higher risk of contamination), the Natural Resources Defense Council (NRDC) indicates that many violations have occurred affecting drinking water.  In fact, the NRDC has indicated that Michigan has violated the Safe Drinking Water Act with 80,000 safety violations that has affected an estimated 77 million people’s drinking water.

A Virginia Tech professor Marc Edwards explains the insurgence of the bacteria into the public water supply stems from iron found in nearby river water.  “What we discovered was that when the Flint River water went into the system it released a lot of iron, and removed the disinfectant from the water,” Edwards said. “And in combination, those two factors, the iron as a nutrient and the disinfectant disappearing, allowed legionella to thrive in buildings where it could not do so previously.”

The Flint water crisis began when state officials made a temporary switch in the water supply, which would not have been a major issue.  The problem was that the water was not treated properly with an anti-corrosive agent.  Edwards explains that the harsh water began to eat away at the pipes as it traveled to people’s homes.  The lead pipes leeched harmful lead into the water, poisoning hundred.  “The triggering event was very clearly the use of Flint River water without any corrosion control,” Edwards said.  “Had the corrosion control been in the water, disinfectant would have been higher, iron would have been lower, probably the outbreak would not have occurred.”

While the situation is Flint, Michigan is an extreme case, maintenance of plumbing is very important to prevent disease of all kinds.  Legionnaires’ is just one of them.

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