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Legionnaires’ disease: What is it and how can you prevent it?

Legionnaires' disease

Legionnaires’ disease, or Legionellosis, is an infection caused by the bacteria Legionella pneumophila. This disease causes symptoms such as high fever, chills, muscle aches, and headaches; however, these can be present in other conditions as well. In more severe cases of Legionnaires’ disease, pneumonia can develop and spread to other parts of the body, leading to serious complications and even death.

What is Legionnaires’ disease:

Legionnaires’ disease (legionellosis) is a respiratory illness caused by Legionella bacteria. In most cases, people contract legionellosis after inhaling microscopic airborne water droplets containing Legionella bacteria. The source of these bacteria may be present in soil or potting mix, such as in a whirlpool spa, hot tub or cooling tower.

The risk of getting Legionella infection increases in places where there are large groups of people, including hospitals, hotels, college dormitories and long-term care facilities. People with a weakened immune system (such as cancer patients or people taking certain medications) have an increased risk for infection.

Symptoms include fever, cough, shortness of breath and muscle aches. If left untreated, legionellosis can be fatal.

How common is Legionnaires’ disease?

Legionnaires’ disease is a serious type of pneumonia caused by bacteria called Legionella. This bacteria thrives in warm water, such as air-conditioning units, hot tubs, cooling towers or evaporative condensers in large buildings.

It’s commonly spread through droplets that come from coughing or sneezing. It affects only about 2,000 people a year in Europe and North America combined, but most of those who contract it are elderly with weakened immune systems.

Although these bacteria are naturally occurring, outbreaks do occur from time to time. Those most at risk of contracting Legionnaires’ disease are people who travel to other countries or areas where there have been outbreaks in recent years.

In 2016, a traveler was diagnosed with Legionnaires’ disease after visiting Tunisia, but then spread back to France, infecting another 7 people.

Legionnaires’ disease symptoms usually appear within 2 to 10 days of exposure. Most people will experience flu-like symptoms, including a cough, fever, chills and muscle aches. Occasionally, more severe complications may develop.

Who is at higher risk?

Legionnaires’ disease is a severe form of pneumonia, which means it affects your lungs. It is caused by a type of bacteria called Legionella pneumophila. People most commonly get sick if they breathe in small droplets of water containing Legionella bacteria.

These droplets come from sources such as cooling towers, whirlpool spas, hot tubs, humidifiers, decorative fountains or large plumbing systems that continuously circulate water.

Legionella bacteria are found in most natural sources of water. When small droplets from these sources come into contact with a person’s mouth, nose or eyes, that person may become sick. Exposure usually occurs when people breathe in very small droplets that get into their lungs.

Legionella bacteria are not spread from one person to another through casual contact like touching or shaking hands. Also, Legionnaires’ disease cannot be spread directly from animals to people.

Legionella bacteria grow best in warm water, such as water temperatures between 22 and 104 degrees Fahrenheit. Water becomes a potential source of exposure when that water travels through cooling towers, whirlpool spas, hot tubs, humidifiers or large plumbing systems that continuously circulate water.

Those infected may get sick if they breathe in very small droplets of contaminated water in any setting. The disease cannot be spread directly from person to person through normal contact like shaking hands or hugging.

Signs and symptoms:

The earliest symptoms of Legionnaires’ disease may include headache, high fever, chills, aching muscles, loss of appetite, general malaise and coughing. These symptoms occur 2 to 10 days after exposure to Legionella bacteria.

Possible complications include pneumonia and respiratory failure. Antibiotics usually clear up Legionnaires’ disease in six weeks or less. However, if left untreated it can be fatal in as little as five days.

It’s also possible to be infected with Legionella bacteria but show no symptoms of illness. However, since you may pass Legionella bacteria to others if infected, it’s important to seek medical attention immediately if your physician thinks Legionnaires’ disease is a possibility.

Your doctor will conduct a physical exam, which may include listening to your lungs with a stethoscope for telltale signs of pneumonia. He or she also may order blood tests or take x-rays for more evidence.

The U.S. Centers for Disease Control and Prevention (CDC) estimates that between 8,000 and 18,000 people in the United States contract Legionnaires’ disease each year. According to a recent report from that agency, almost half of these infections happen in healthcare settings such as hospitals, nursing homes or outpatient facilities like dialysis centers.

The CDC reports that, in 2015, 149 people died from Legionnaires’ disease in the United States. Eighty-five percent of these deaths occurred in people who were at least 65 years old.

Risk factors:

If a person smokes, they are 20 times more likely to develop Legionnaires’ Disease. If they have chronic lung disease, they may be at even greater risk. Many people who get Legionnaires’ also drink alcohol, or take medicines that cause fever. These risk factors increase your chances of developing Legionnaires’ disease and should be avoided as much as possible.

The infection usually comes from breathing in water vapor containing legionella bacteria. The disease cannot be spread from person to person. The CDC has confirmed that it does not come from eating contaminated food, nor drinking tap water.

Legionella is found naturally in freshwater lakes, rivers, streams, ponds and hot springs. In fact about 20% of natural freshwater sources contain Legionella bacteria. According to EPA regulations at least 10% of city systems must also be positive for Legionella to comply with safety standards for public health.

The treatment of Legionnaires’ depends on its severity. If there are no symptoms, only laboratory tests will show if a person has been infected. Treatment involves antibiotics such as Zithromax or Azithromycin.

Prevention methods:

Legionnaires’ disease is a potentially fatal respiratory illness that’s caused by exposure to waterborne bacteria called Legionella. The illness has several symptoms, including cough, fever, muscle aches, confusion and headaches. To avoid contracting Legionnaires’ disease and other similar illnesses from contaminated drinking water, consider installing a whole-house filter. Filters not only remove harmful contaminants from your tap water but also improve its taste and smell.

If you’re already at risk for Legionnaires’ disease because of your age or a weakened immune system, consider installing a whole-house filter to remove additional contaminants from your tap water. When purchasing a filter, check its NSF/ANSI certification to ensure that it removes Legionella.

The CDC recommends that all American households, particularly those with an elderly or otherwise ill resident, use a whole-house water filter to reduce their risk of infection. A filter removes additional contaminants like chlorine which can irritate skin and eyes.

Filters also improve tap water’s taste, odor and clarity. You should change your water filter at least once every six months depending on local drinking water regulations. Contact your local municipality for more information about changing filters in your area.

The good news is that a whole-house filter will keep your tap water safe. However, regular testing of your drinking water with a home water test kit like those available from Eartheasy ensures that there are no contaminants in your drinking water at any time.

Legionella contamination can affect both large water systems such as hospitals, hotels and apartment buildings, as well as small scale, residential water systems. If you want to avoid contracting Legionnaires’ disease or other illnesses caused by contaminated drinking water, consider installing a whole-house filter to purify your tap water.

How to treat Legionnaires’ disease?

There is no effective treatment for Legionnaires’ disease. People who are at risk of contracting it should take measures to ensure they don’t become infected with Legionella bacteria. A good way to do that is to ensure their water systems are regularly cleaned, disinfected, and checked by a professional. They should also avoid areas where they may be exposed to airborne droplets such as air-conditioning vents or fountains.

The best way to treat Legionnaires’ disease if it has been contracted, is to visit a doctor immediately. If they suspect that you have contracted Legionella, they will take blood samples and perform tests on them. These tests will help them identify exactly which type of Legionella bacteria caused your infection.

For people who are at risk of contracting Legionnaires’ disease, in places where they may be exposed to airborne droplets such as air-conditioning vents or fountains, there are measures they can take to reduce their risk.

These include avoiding areas where there may be a high concentration of bacteria in water such as spas, fountain nozzles, hot tubs, cooling towers, decorative fountains and evaporative condensers. Air conditioning units should also have regular maintenance checks done on them.

To reduce their risk, they should also ensure that their water systems are regularly cleaned, disinfected, and checked by a professional. This will ensure that any bacteria present in fountains or cooling towers is eliminated before they become airborne.


Legionnaires’ disease, one of a group of respiratory illnesses known as atypical pneumonia, causes symptoms including fever, chills, cough, muscle aches and headaches. It’s a severe form of pneumonia caused by Legionella bacteria and spread through inhaling contaminated water vapor. Because these bacteria thrive in warm water, Legionnaires’ has become increasingly prevalent in recent years due to growth in air conditioning use.

Legionnaires’ symptoms usually develop within 2 to 14 days after exposure, but some people take as long as 10-30 days to show signs of illness. The effects of Legionella infection are most severe for older adults, people with weakened immune systems or chronic lung conditions, such as asthma or emphysema. Anyone who experiences a persistent cough should see a doctor immediately. Treatment will include antibiotics from your primary care physician or an infectious disease specialist in conjunction with supportive therapy for pain relief and fever reduction.

The best way to avoid Legionnaires’ disease is by preventing infection. That starts with turning down your hot water heater to no more than 120 degrees F, or 130 degrees F if your system doesn’t have a hot water recirculation pump. A steamy shower or bath at temperatures lower than 120 degrees shouldn’t increase your risk of contracting Legionnaires’ since bacteria are killed at 158 degrees F.


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