Legionella Legionnaires' disease from urine

Test for infection of Legionella pneumophila antigen from urine.

The number of people who have contracted Legionnaires' disease has gradually increased over the past six years. Legionnaires' disease is caused by the legionella bacteria.

In 2016, there was a record number of people with Legionnaires' disease in the Netherlands: 324. Twenty of them died. In the two years before, there were 273 and 214 people who became ill. In both years, thirteen people died from the effects of the disease.

Legionella bacteria develop best in warm, stagnant water. If that water is misted, for example in fountains or garden sprinklers, people can become infected. The bacteria are then inhaled and end up in the lungs. There the bacteria can cause pneumonia, also known as Legionnaires' disease. This can be fatal. From drinking contaminated water, people cannot get sick.

Due to increasingly wet and warm weather, the number of infections in the Netherlands is rising.

The detection of Legionella antigen in urine has become by far the most requested laboratory test for the diagnosis of Legionnaires' disease in recent years. Urine antigen tests are simple, quick to perform, and specific. Since the antigen is present in the urine early in the course of the disease, often as early as the third day of clinical symptoms, early diagnosis is possible. The tests are particularly aimed at detecting antigens of L. pneumophila serogroup 1.

The sensitivity of the tests depends on the severity of the clinical picture and ranges from 50 to more than 90%. In severe cases of legionella pneumonia, the urine antigen test is usually positive. A negative test can be found in less severe cases or in legionella infection from a serogroup other than serogroup 1. Some blood tests can also detect antigens from serogroups other than legionella pneumophila and serogroup 1.