Legionella grows in water at temperatures between 20°C and 50°C. Below 20 °C it remains dormant, and does not survive above 60 °C.
Legionella infection is an environmental disease produced by a gram-negative bacterium of which there are more than 58 species and 70 serogroups. Legionella pneumophila serogroup I causes between 85-90% of all legionella infections.
How Is It Transmitted?
Fresh water is the main reservoir of the bacteria, the optimal conditions for its development being stagnant water, temperatures between 25 and 45ºC, and the presence of sediments.
It is estimated that hospital water systems have a high colonization by legionella, which is why it is a relatively common type of infection in hospitals.
Transmission to humans occurs when fresh water containing these bacteria enters a building’s plumbing system. The infection is contracted by inhaling contaminated water droplets through shower water, irrigation, decorative fountains, hot tubs, or cooling water circuits for air conditioning. Legionella disease is not spread from person to person.
What Are The Symptoms?
- Legionella infection can give rise to two different clinical pictures: Pontiac fever and legionella pneumonia or Legionnaires’ disease; Both pictures can occur sporadically or in outbreaks.
- The incubation period for Pontiac fever is between 5 to 66 hours, and that of Legionella pneumonia is between 2 to 10 days.
- Pontiac fever presents as a catarrhal condition without pulmonary involvement, self-limited, and usually lasting for a week.
- Legionella pneumonia is virtually indistinguishable from other pneumonia and usually presents with high fever, chills, general malaise, muscle aches, headache, confusion, non-productive cough, and/or gastrointestinal disturbances such as diarrhea, nausea, vomiting, or abdominal pain.
How Is It Diagnosed?
- The diagnosis of Pontiac fever is usually made based on the symptoms presented by the patient, in most cases the causative agent is not identified since legionella infection is confused with any other similar catarrhal process.
- The diagnosis of legionella pneumonia is made based on clinical criteria (the patient presents compatible symptoms) and laboratory criteria: samples of blood or fluid from the lungs are taken and sent to the laboratory for culture and identification. of the bacteria. Other useful tests for diagnosis can be PCR techniques in respiratory samples or the search for antigens against the bacteria in urine analysis. A chest X-ray is required, which usually confirms the presence of lung involvement.
When the infection occurs in the form of an outbreak, the diagnosis should be suspected in people who present compatible symptoms and share the same building or in patients admitted to the hospital for another reason and who develop fever and/or pneumonia during admission.
Legionella Treatment
- Pontiac fever usually does not require specific treatment except for the control of the patient’s symptoms, and it usually self-limits within a week.
- Legionella pneumonia requires specific treatment with oral and/or parenteral antibiotics against highly negative bacteria, and life support measures and control of the symptoms that the patient presents; the usual duration of the infectious picture is 1 to 2 weeks. In severe cases, it is necessary to hospitalize the patient for correct treatment.
Community-acquired Legionella pneumonia usually responds well to treatment when diagnosed early in the infection and appropriate antibiotic treatment is prescribed. Hospital-acquired pneumonia, however, has a high mortality rate as it is usually treated in more resistant forms and affects patients with comorbidities.
How To Prevent?
Good control of water reserves is required by the health authorities, neighboring communities, and hospitals.
What you should know…
- Fresh water is the main reservoir of the bacteria, the optimal conditions for its development being stagnant water, temperatures between 25 and 45ºC, and the presence of sediments.
- Legionella infection can give rise to two different clinical pictures: Pontiac fever and legionella pneumonia or Legionnaires’ disease; Both pictures can occur sporadically or in outbreaks.
- Good control of water reserves is required by the health authorities, neighboring communities, and hospitals.
