Legionnaires’ disease is one of those illnesses that usually has people scratching their heads. Most don’t understand what the disease is, or what it does to victims. That, however, is starting to change, as the disease becomes more commonplace and newsworthy.

Here are some frequently asked questions – and their corresponding answers – about Legionnaires’ disease:

What is Legionnaires’ disease? Legionnaires’ disease – also called Legionellosis and Legionella pneumonia – is a severe type of pneumonia or lung infection. According to the Centers for Disease Control and Prevention (CDC), health departments reported nearly 10,000 cases of Legionnaires’ disease in the United States in 2018. Because the disease is underdiagnosed, this number is more likely to be 2.5 times greater. In any case, 10 percent of those infected will die from the infection.

How do you contract Legionnaires’ disease? Legionella bacteria are contracted by inhaling microscopic water droplets in the form of mist or vapor. The bacteria grow best in warm water and are found primarily in human-made environments. Outbreaks have been linked to a range of sources, such as:

• cooling towers in air conditioning systems
• decorative fountains
• mist machines in grocery stores’ produce sections
• hot tubs and whirlpools at fitness centers and on cruise ships
• hot water tanks and heaters
• large plumbing systems
• showers and faucets
• swimming pools
• equipment used in physical therapy
• water systems like those used in hotels, hospitals, and nursing homes.

People also can catch Legionnaires’ disease by the aspiration – a condition in which food, liquids, saliva, or vomit is inhaled into the airways – of contaminated drinking water. It’s also possible to contract Legionnaires’ disease from home plumbing systems, although the great majority of outbreaks have occurred in large buildings, because complex systems allow the bacteria to grow and spread more easily.

How is Legionnaires’ disease diagnosed? The symptoms of Legionnaires’ disease look like other forms of pneumonia or even the flu, which is why so many cases go unreported. Early symptoms can include:

• chills
• fever (potentially 104 degrees or higher)
• headaches
• loss of appetite
• muscle aches.

After the first few days of the disease presenting, symptoms can worsen to include:

• chest pain when breathing (called pleuritic chest pain, due to inflamed lungs)
• confusion and agitation
• a cough, which may bring up mucus and/or blood
• diarrhea (about one-third of all cases result in gastrointestinal problems)
• nausea and vomiting
• shortness of breath.

The incubation period – the amount of time between breathing in the bacteria and developing symptoms – is usually 2 to 10 days after exposure and can be as much as 16 days. On average, however, the incubation period is 3 to 6 days.

(Note: There is also a mild form of Legionnaires’ disease called Pontiac fever, which can produce symptoms including a fever, chills, headache, and muscle aches. Pontiac fever doesn’t infect the lungs, however, and symptoms usually disappear within two to five days.)

What are the complications of Legionnaires’ disease? After Legionnaires’ disease has been diagnosed, hospitalization is often necessary. In the most severe cases of Legionnaires’ disease, complications can include respiratory failure, kidney failure, septic shock, or even death.

Are you at risk of contracting the disease? Anyone can get the disease, but those at the greatest risk of infection include:

• people 50 years old or older
• smokers (current or former)
• heavy drinkers of alcohol
• people with chronic lung disease, such as chronic obstructive pulmonary disease or emphysema
• people with weakened immune systems (those suffering from diseases such as diabetes, cancer, kidney failure, or infected with HIV)
• organ-transplant recipients
• individuals following certain drug protocols (for instance, corticosteroids)

Even relatively healthy individuals have been known to contract the disease, although less typically.

Why is it called Legionnaires’ disease? In July 1976, more than 4,000 delegates to the American Legion Convention gathered at Philadelphia’s Bellevue-Stratford Hotel. Several days after the four-day event, many attendees became sick. By Aug. 2, more than 20 attendees were dead, and hundreds were experiencing pneumonia-like symptoms. The final case count reached 221, and 34 of those died.

It wasn’t until months later that the bacterium was identified and isolated and found to be breeding in the cooling tower of the hotel’s air conditioning system.

Sources: CDC.com, epa.gov, osha.gov, eddmprnews.org, legionella.org, mayoclinic.org, patient.info, hcinfo.com, healthline.com, medscape.com

Image: Agence France-Presse