LEGIONELLA What is it and how does it affect us
What is the Legionella bacteria?
It is a group of bacteria widely spread in nature which need a damp atmosphere and heat (between 32ºC and 45ºC) to live and grow. Its natural habitat is water: rivers, lakes, streams and thermal water. It can also be found in contaminated artificial environments, such as humidifiers, cooling towers, drinkable water supplies, etc.
There are about 40 different species of legionella bacteria. The most harmful specie is the so called Pneumophile. Within this specie there are 15 different Serogroups. Serogroup 1 is responsible for the legionnaire’s disease.
Serogroup 1 has three subgroups: Pontiac, Olda and Bellingham. The Pontiac subgroup causes the 85% of the legionnaire’s disease.
What type of infections does it produce?
The legionella bacteria usually causes two types of infections, both regularly caused by the pneumophile, serogroup 1. These two diseases are:
1.- Pontiac’s fever: this type is less serious and the most frequent, it resembles a flu, it does not cause pneumonia, it is self limited, it progresses positively and the full recovery occurs within a week.
2.- Legionnaire’s disease: it was described for the first time in 1947 and the first outburst appeared in 1965 in a psychiatric hospital in Washington, U.S.A. It was named like that because it affected the participants in an American Legion meeting at Philadelphia in 1976. This disease causes a pneumonia and it affects the general well-being. It is the most serious form. The majority of the cases appear sporadically (over 80% of the cases), and the epidemic outbreaks are a lot less frequent.
What are the symptoms of the legionnaire’s disease?
The legionnaire’s disease incubation period ranges between two to ten days; this is the time it takes for the symptoms to appear after having been exposed to the bacteria.
The patient might feel tired and weak for a few days. The majority of the patients taken into hospital develop a high fever, even over 39ºC. Severe coughing can be the first indication of lung infection. Many patients suffer with gastrointestinal pains, diarrhoea, nausea and vomiting. Other common symptoms include headache, muscular pain and difficult breathing.
Who are at risk?
Although anyone can contract the disease, it preferably affects people who have a higher risk of contracting an infection by the legionella bacteria. They are elderly people or people with weakening illnesses ( people with heart, lung, kidney or diabetes conditions, etc), smokers with a low immune system or being treated with immune suppressant drugs (they diminish the defences).
Children are at little risk, although it is less frequent to contract the disease at that age. It even goes unnoticed. There are very few registered cases of serious infections in children.
How is the disease contracted?
The most known theory is that the way to get infected is via water drop aerosols which contain the legionella bacteria and are inhaled by the person. These drops come from reservoirs infected with the legionella bacteria, these could be refrigeration equipments, humidifiers, showers, sprinklers, ornamental fountains, etc.
Nevertheless, there is new evidence that suggests a different more common way of getting infected. “Aspiration” is the easiest way for the bacteria to enter the lungs and causing pneumonia. Aspiration is produced when, due to choking, the mouth secretions go wrongly into the lungs instead of going towards the oesophagus and stomach. The mechanism to protect against the “Aspiration” does not function in patients who smoke or who have lung illnesses.