Generally patients with Legionnaires' disease develop fever, chills, and cough that may be dry or produce sputum [6]. In some patients muscle aches, headaches, loss of appetite, diarrhea and tiredness may also be seen.

Legionnaires' disease can also lead to severe pneumonia with dyspnea in some patients. In some cases it may lead to the development of adult respiratory distress syndrome. Bradycardia may also occur as a result of the fever that accompanies this condition.

The presentation for Legionnaire’s pneumonia is not distinctive as it closely relates to what is obtainable with other forms of pneumonia like Chlamydia pneumonia and Mycoplasma pneumonia.

In people with Pontiac fever, a self-limiting influenza-like illness with fever, chills, headache and muscle aches is seen but pneumonia is rare. Individuals affected often recover within 5 days without receiving any treatment.

Diagnostic tests are the backbone of diagnosis as these points out bacteria in sputum, presence of Legionella antigens in urine samples as a result of renal fibrosis and the presence of Legionella antibody levels in blood samples [7]. A urine antigen test is the most successful diagnostic test. This is because it detects Legionella pneumophila serogroup 1 which accounts for 70% of disease.

Other laboratory findings seen in patients with Legionnaires' disease include the following [8]:

• Elevated liver enzyme levels
• Highly elevated erythrocyte sedimentation rate (ESR)
• Highly elevated ferritin levels
• Increased C-reactive protein (CRP) levels (>30 mg/L)
• Hypophosphatemia (specific to Legionnaires' disease excluding other causes of hypophosphatemia) [9]
• Microscopic hematuria
• Proteinuria (40%)

Use of antibiotics and some of the newer macrolides are the current treatment of choice. The antibiotics that are used the most frequently are levofloaxacin and azithromycin [9]. The antibiotics are very effective as they have excellent intracellular penetration in cells that are infected with Legionella pneumophila.

As mentioned above, majority of people that become exposed to Legionella pneumophila do not go beyond the Pontiac fever phase. However, the condition can be life-threatening [5]. The risk of dying is highest in patients who have chronic conditions and those that get infected while on admission in a hospital.

The chief cause of death in patients is progressive respiratory failure. However, mortality rate is dependent on the patient’s comorbid conditions as well as the choice of antibiotics and the amount of time taken to begin treatment.

The legionellosis condition is chiefly caused by the bacterium Legionella pneumophila [2]. There are two distinct stages of this disease.

Pontiac fever is a milder illness which develops between a few hours and two days after initial infection. It generally resolves spontaneously.

Legionnaires' disease stage is the main stage of the infection and may involve pneumonia. This form of the disease generally kicks in two to 10 days after initial infection but its onset may be delayed by over two weeks. The disease got its name in 1976 following a pneumonia outbreak that hit individuals attending an American Legion convention of that year.

Legionnaires' disease is not rare but it is not uncommon either. Over 4% of all community-acquired pneumonia is as a result of it [3]. The number of people that develop Pontiac fever is also unknown as majority of such individuals only develop very mild symptoms.

Individuals likely to develop Legionnaires' disease after a Pontiac fever episode are those aged 50 and above, those that smoke or have chronic lung disease and immunosuppressed individuals.

Legionnaires' disease is generally acquired by inhalation [4]. In some cases, it can be acquired by microaspiration of water that has been contaminated. In the lungs, the causative organism is phagocytosed by macrophages in the alveoli. This leads to the release of virulent factors that makes it possible for them to no just survive but also replicate in the individual. In individuals with this disease, the alveoli are filled with bacteria, neutrophils, microphages as well as erythrocytes.

The pathogenesis for Pontiac fever is not clear but it is equally caused by the inhalation of Legionella pneumophila. 

To prevent outbreaks of Legionnaires' disease, pools, spas and other water systems have to be cleaned meticulously [10].

To further lower risk of infection, it is important for individuals to avoid smoking. Smoking increases chances of developing Legionnaires' disease as soon as the human body is exposed to Legionella pneumophila.

Legionnaires' disease is a condition also known as legionellosis. It is caused by a bacterium which lives mostly in the mist found typically in air-conditioned spaces [1]. This is why the bacterium has been able to infest entire buildings in many cases.

Another variation of the condition is Pontiac fever but Legionnaires' disease is more severe and if neglected, is ultimately fatal. People with Legionnaires' disease develop fever, chills and cough as the disease progresses. In its most advanced state, the disease can lead to severe pneumonia and respiratory failure. Antibiotics are useful in combating the condition but prevention is the most useful approach.

Legionnaires’ disease is an infection, often accompanied by pneumonia. Pneumonias refer to the inflammation of the lungs and in the case of Legionnaires’ disease it is caused by a bacterium known as Legionella pneumophila.

It is not possible to contact this disease from person-to-person contact. As majority of people get this disease by inhaling the bacteria. Older individuals, smokers and people with weak body defences have the highest risk of contracting the disease.

Another disease caused by the Legionella pneumophila is Pontiac fever. Pontiac fever is a milder illness and can occur separately or in combination with the Legionnaires’ disease in people infected with the bacteria. Pontiac fever often clears up on its own without treatment but Legionnaires' disease left untreated may be fatal.

Prompt treatment with antibiotics often cures the disease but follow up is required in some patients as problems may continue after treatment.

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