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All About Legionnaires Disease

Posted On: Dec 26, 2019

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Legionnaires’ disease is a serious and life-threatening condition caused by certain species of bacteria called Legionella. It involves severe lung inflammation leading to breathing difficulty. The risk of death is more in patients with previous medical conditions such as a lung disorder. However, even a previously fit person is likely to die with the disease. The disease commonly occurs in middle-aged or older populations, but can also develop in children in whom the severity is, however, less.

What is the source of infection?

The bacteria do not spread through physical contact but can spread through inhalation through droplets. For example, breathing in the steam during the spa which is not cleaned for use for another person.

Legionella can grow best in warm water for example in cooling towers, hot tubs and water tanks, parts of air conditioning systems, large plumbing systems, etc. Hospital buildings where large water systems are used can be the source of infection if already infected patients are present. They do not grow in the air conditioners of the cars or such small areas.

The disease is more common during the summer and early autumn seasons, but can also occur at any time of the year.

Risk factors for getting the disease

You may be at greater risk of developing the disease if you

  • are older than 65 years of age,
  • are a chronic smoker or abuse alcohol,
  • have emphysema (a chronic lung disease), or pneumonia,
  • have a weak immune system (for example patients with cancer, kidney failure, or diabetes),
  • have undergone transplantation (use of drugs to suppress the immune system in such patients can increase their risk OF the infection),
  • have been using a ventilator for a long time.

How to identify if you have got infected with Legionella

The symptoms develop after 2 to 14 days of exposure to the bacteria. In the initial 4-5 days, the symptoms get worsened which may improve in the next 4-5 days.

Initially, the symptoms of Legionnaires’ disease are similar to most other lung infections, making it difficult to identify the disease in the initial stages. Symptoms may include high fever, shivering, and a dry cough. You may also have muscle or joint pain. The other symptoms which may develop later include

  • Chest pain,
  • Cough with blood. Sputum may become yellow and blood stained,
  • Nausea, vomiting, diarrhea, fever, headache,
  • Abdominal pain,
  • A general discomfort and uneasiness,
  • Shortness of breath, breathlessness and chest tightness.


Your doctor confirms the presence of the bacteria by checking your urine specimen or samples. In people with pneumonia, the bacterial presence can be checked by taking samples from lung tissue, or in the secretions of the lungs such as the sputum. Chest X-rays and blood cultures also show the presence of the bacteria and the antibodies produced against the bacteria.

What is the treatment?

The treatment of Legionnaires’ disease requires the patient to get admitted to a hospital.

Once the disease is identified, the treatment is immediately started with antibiotics to fight the bacteria. Several antibiotics are available for the treatment of the disease, but the choice of the antibiotic is made based on the patient’s tolerance to the medication and his/her clinical status.

Usually, the antibiotics are given intravenously (that is through the veins) and not orally (through the mouth). Generally, a single antibiotic is given. But if it is not certain whether the infection is due to Legionella or due to other microbes, then a combination of antibiotics is given. The antibiotic therapy can last from 1 to 3 weeks based on the recovery of the individual.

The other treatments include the administration of oxygen given through a mask or a ventilator. This is because of the inflammation of the lungs which reduces the breathing ability of the lungs causing a drop in oxygen levels. Thus, the administration of oxygen can make it easy for the lungs to breathe.

Drinking fluids may not be easy for such patients. Therefore, Intravenous fluids are given to overcome dehydration problem

Even after the recovery, you may have symptoms such as a cough, mild shortness of breath, tiredness and poor concentration which may be present for a few weeks or for several months.

Complications if untreated

If the condition is not treated on time, it can lead to the following complications

Severe sepsis – An untreated infection can spread to the other body parts leading to septic shock which is highly fatal.

Respiratory failure – The lungs cannot supply oxygen to the body parts without external aid (such as the ventilator or breathing tubes).

Acute kidney injury – In the advanced stage of the disease, the kidneys cannot filter the blood properly, and the toxic materials get accumulated in the body.

How to prevent the infection?

Prevention is mainly at the level of design and maintenance of the cooling towers and water systems. Maintain the water temperature either below 20oC or above 60oC while working with large water supplies. At this temperature, the bacteria cannot survive in the water. Ensure to keep the water clean and do not allow stagnant water in your premises. Decontaminate water with monochloramine or by superheating.

At present, there is no vaccination available against the bacteria.

Most of the people exposed to the bacteria do not develop Legionnaires’ disease. But if you think you have the symptoms of the disease, then you must immediately consult a physician. Earlier the identification of the disease better is the outcome with the treatment.


  1. https://www.cdc.gov/legionella/about/
  2. https://legionella.org/about-the-disease/what-is-legionnaires-disease/
  3. Isenman HL, Chambers ST, Pithie AD, MacDonald SL, Hegarty JM, Fenwick JL, Maze MJ, Metcalf SC, Murdoch DR. Legionnaires’ disease caused by Legionella longbeachae: Clinical features and outcomes of 107 cases from an endemic area. Respirology. 2016 May 19. [Epub ahead of print]
  4. Borella P, Bargellini A, Marchegiano P, Vecchi E, Marchesi I. Hospital-acquired Legionella infections: an update on the procedures for controlling environmental contamination. Ann Ig. 2016 Mar-Apr;28(2):98-108.

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