Legionnaires' disease more prevalent than previously thought – study

By Besa Chembo

Researchers at the University of Otago discovered that the number of cases of Legionnaires' disease was three times higher than previously thought.

Legionella longbeachae is commonly found in soil and composted plant material.
Photo: 123rf.com

Legionnaire's disease burden in New Zealand (LegiNZ), a study funded by the New Zealand Health Research Council, found that many cases were undiagnosed and under-reported because patients with Legionnaires were not present distinctive symptoms badociated with other forms of pneumonia.

Legionnaires are a serious form of pneumonia caused by a bacterium. In 63% of cases, it is a bacterium called Legionella longbeachae, which is commonly found in soil and composted plant material.

From May 2015 to May 2016, researchers organized a specialized test for the detection of legionellosis in people hospitalized for pneumonia throughout New Zealand. Three times more cases were diagnosed than the average of cases confirmed three years earlier.

More than 20 hospitals participated and tested 4862 patients with hypostasis using a PCR test, detecting 197 cases through direct tests and 41 other cases through a notification system. mandatory. A total of 238 cases, or 5.4 cases per 100,000 New Zealanders, required hospitalization.

The study aimed to improve the identification of cases of legionnaires in patients with pneumonia. Many cases of "life-threatening and preventable" bacteria are not detected due to the inconsistent use of diagnostic tests and uncertainty in the choice of the tester.

According to clinical microbiologist and Dean of Otago University, David Murdoch, in New Zealand, the incidence of Legionnaires' disease is the highest in the world. This is explained by the fact that the tests carried out by New Zealand are more extensive than anywhere else in the world.

"The results are relevant for other countries because the bacteria at the origin of legionellosis is present internationally, but few countries have implemented routine tests."

Professor Murdoch said that the polymerase chain reaction (PCR) test was the best way to diagnose legionnaires because the other tests could not differentiate it from other forms of pnuemonia.

Hawke's Bay, Bay of Plenty and Waitematā had the highest rates of the disease, with eight cases per 100,000 population, most cases being underreported in previous years.

Canterbury also had high rates of between six and eight cases per 100,000 population, but its claims are more accurate because it adapted the PCR test in 2010 and is therefore the most comprehensive test for the disease in New Zealand.

As a result, the number of legionnaires reported is the highest in the country and accounts for one third of national case notifications, while it accounts for less than 10% of the total population of the country.

Professor Murdoch said the PCR test was crucial for and that he supported its systematic use to detect and ensure access to appropriate treatments.

"The sooner the infection is treated with a specific bacterial drug, the better the prognosis."