Definition of legionellosis
In medicine, "Legionelliosis" is a general term that indicates all the various types of infection generated by obligatory aerobic gram-negative bacteria belonging to the genus Legionella .
Clinical forms
See also: Legionellosis symptoms
We have seen that "legionellosis" is a general term, which includes three clinical forms of legionella infection. Erroneously, legionellosis tends to be associated only with Legionnaires' disease, the most dangerous and most severe clinical form, but there is also a pseudo-flu (Pontiac fever) and sub-clinical form of Pontiac fever.
- Legionnaires' disease
Among the various forms of legionellosis, Legionnaires 'disease is undoubtedly the most dangerous and the most severe in terms of symptoms and risks: in fact, it is estimated that the mortality linked to Legionnaires' disease is around 10% and, in cases more serious, the fatality rate is almost 50%.
This legionellosis appears as an acute pneumonia, very similar to the classic flu forms that affect the lower respiratory tract: all this represents a serious limit for the diagnosis, therefore for the timely recognition of the disease. In this regard, Legionnaires' disease is often underestimated precisely because it is misdiagnosed.
The incubation period of the bacterium is variable, but generally does not exceed 10 days; this legionellosis begins, precisely, with the typical flu symptoms, such as general malaise, high fever, headache, myalgia and wheezing. Respiratory failure and pulmonary abscess are two possible but infrequent complications. Almost absurdly, when the aforementioned form of legionellosis triggers more serious problems, such as neurological, gastric, intestinal and renal disorders, the patient's chances of recovery increase because the diagnosis is simpler and unambiguous; consequently, the therapies are targeted and precise.
Among the most useful therapies, the administration of erythromycin and rifampicin, antibiotics useful for reducing the severity of symptoms and for reducing the risk of mortality, stands out. Therapy should be continued for at least three weeks in order to avoid relapses.
A recently proposed cure is the one with fluoroquinolones, but some years will have to wait for the confirmation or not of the efficacy of these molecules.
Penicillin, chloramphenicol, aminoglycosides and tetracycline therapies have proved to be in vain and ineffective.
- Pontiac fever (acute form) : so named in memory of the acute febrile epidemic that occurred in 1968 in Pontiac, Michigan. This legionellosis is a mild flu-like form, generally non-fatal (benign) but extremely contagious. The symptoms, which do not affect the lung, begin after 1 or 2 days following infection: the patient complains of high fever, chills, malaise, headache, sore throat and cough. In most cases, Pontiac fever resolves spontaneously in 2-5 days, without the need for specific treatments or treatments. It is scientifically proven that Pontiac fever is supported by Legionella pneumophila ; however, also L. micdadei and L. feelei are possible etiological elements that are not fully demonstrated.
- Pontiac fever (sub-clinical form): this legionellosis, even less serious than the previous ones described above, presents itself without some clinical symptoms, therefore it does not include pulmonary involvement and typical flu symptoms. The sub-clinical form of Pontiac fever can only be diagnosed with the detection of anti-Legionella spp.
Incidence and prevention
Given the serious health problem caused by the various forms of legionellosis, the WHO has placed these infections under surveillance. It is estimated that legionellosis affects 8, 000-18, 000 subjects every year: a clearly very wide range, an indication of the fact that the recognition of legionellosis is not always immediate, in particular Legionnaires' disease.
An increasing number of countries have begun promoting surveillance and control programs for the prevention of legionellosis.
The incidence of Legionella infections (estimated at around 1, 000 patients each year) is still underestimated in our country: Healthcare aims to encourage and improve preventive measures aimed at containing Legionella contamination [taken from // www.legionellaonline.it/]
