Legionnaires disease has an incubation period of 2 to 10 days (but up to 16 days has been recorded in some outbreaks).
Untreated Legionnaires disease usually worsens during the first week.
Early diagnosis greatly increases the chances of a successful recovery. Due to the complexities in detecting the bacteria (it is not a simple test), it also has to be assumed that there is a certain number of undetected cases. In addition, many cases of Legionellosis may simply not be tested for the Legionella bacterium, due to the symptom’s resemblance of pneumonia.
Early symptoms of Legionnaires disease are similar to ‘flu’ symptoms and include headache, fever, chills, muscle aches & pains, a dry cough & shortness of breath.
Most common symptoms are:
|Fever (>39 centigrade)||70%|
|Myalgia, muscle pain||38%|
Death occurs through progressive pneumonia with respiratory failure and/or shock and multi-organ failure, particularly kidney failure.
A certain part of the general population are vulnerable to Legionella. Vulnerability is increased if there are factors that reduce the response immune systems such as, for example, a cold.
Recovery always requires extensive antibiotic treatment, and is usually complete after several weeks or months. In rare occasions, severe progressive pneumonia or ineffective treatment for pneumonia can result in brain sequelae.
The death rate as a result of Legionnaires disease depends on: the severity of the disease, the appropriateness of initial anti-microbial treatment, the setting where legionella was acquired, and host factors (for example, the disease is usually more serious in patients with immuno-suppression).
The death rate may be as high as 40–80% in untreated immuno-suppressed patients, though can be reduced to 5–30% through appropriate case management and depending on the severity of the clinical signs and symptoms. Nevertheless, full recovery can be slow and take months, often with the patient never fully returning to precondition health.
This is why, when it comes to Legionnaires disease, the most effective way of dealing with the affliction is prevention.