Legionnaire’s Disease

Outbreaks of Legionnaire’s Disease often hit the headlines, and a recent outbreak in Edinburgh, Scotland, was no exception in the UK press. What is Legionnaire’s Disease, how is it caused, and how can it be prevented?

What is the cause of Legionnaire’s Disease?

In July 1976, 251 people who attended a convention of the American Legion at the Bellevue-Stratford Hotel in Philadelphia, USA, became ill with high fevers and pneumonia; 34 of those afflicted with the disease later died. The disease was found to be caused by infection with a previously undiscovered species of bacterium, which scientists named Legionella, hence the pneumonia-like condition was named Legionnaire’s Disease.

After extensive scientific research, the Legionella bacterium was found to thrive in warm waters at an optimum temperature of 35°C (95°F). It is found commonly in lakes and rivers, but most infections of Legionella occur when people inhale aerosols (small droplets) of infected water, particularly from sources such as large central air conditioning systems, showers, spas and ice-making machines – all features commonly found in hotels, on board cruise ships and in prisons, where the majority of outbreaks have historically taken place. Infected aerosols emitted from the cooling towers of power stations or chemical plants are another frequent source of Legionella, and bacteria from these towers have been recorded to spread within a 6km radius of the source, thus potentially worsening the extent of the outbreak.

What are the symptoms of Legionnaire’s Disease?

Legionnaire’s Disease is characterized by respiratory infection leading to pneumonia, which can be accompanied by a dry or chesty cough, a high temperature, fever and chills. Some people also experience muscle aches, headache, tiredness, confusion, loss of co-ordination, diarrhea and vomiting, and the disease can be fatal. It can take 2-10 days for the bacteria to grow to sufficient numbers in the body to make you ill, so symptoms can take some time to appear. Some people infected with Legionella experience a milder form of Legionnaire’s Disease called Pontiac Fever, which presents with fever and headaches but is not often life-threatening. The symptoms of Pontiac Fever usually take only a few hours to appear, and recovery usually occurs within a few days, even without treatment.

Who is at risk of Legionnaire’s Disease?

There are now strict regulations in most countries that force companies such as hotels and factories to carry out regular Legionella testing and decontamination procedures, so fortunately it is now relatively rare to contract Legionnaire’s Disease. People who work in locations where Legionnaire’s Disease is more common are at higher risk; nevertheless the risk is low if the employing organization adheres to the decontamination regulations. A research study conducted in the UK in 2010 found that that people who drive commercial vehicles for a living were 5 times more likely to contract Legionnaire’s Disease than other drivers; after further investigation, it was discovered that vehicle windshield washers can be a source of infection if pure water is used as a washing agent rather than a washing fluid.

As with most infections, Legionnaire’s Disease tends to hit the elderly hardest, as they have weaker immune systems that are less able to fight off the infection naturally. Similarly, young children with under-developed immunity, and people with weakened immune systems through pregnancy or immunosuppression, are also more at risk of contracting a fatal disease in incidental cases of Legionella outbreak. Since Legionella primarily targets the lungs, people who smoke, or who have lung or respiratory diseases, are far more likely to become ill than those with healthy lungs.

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Lisa Martin

Lisa Martin is a qualified biology teacher and experienced freelance science writer from Warwickshire in the UK. She is fascinated by how the human body works and is particularly interested in writing about new research and discoveries in science and medicine.

Follow Lisa on Twitter: lisaamartin1

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