After introducing routine polymerase chain reaction testing on all specimens of patients with pneumonia, researchers found that legionnaires’ disease is a greater burden in New Zealand than previously thought.
“We knew that legionnaires’ disease was common in our region, but we're concerned that many cases were undetected and that laboratory testing was not always done properly,” David Murdoch, MD, professor and head of pathology at University of Otago, Christchurch and clinical microbiologist at Canterbury Health Laboratories, both in New Zealand, told Infectious Disease News. “We also realized that clinicians were unable to accurately identify the group of patients with pneumonia who were most likely to have legionnaires’ diseases, so a routine PCR testing strategy seemed appropriate.”
Murdoch and colleagues compared the number of hospitalized patients with legionnaires’ disease from November 2008 to October 2010 with the number of patients identified from November 2010 to October 2012, the 2-year period after a PCR testing strategy was introduced. All respiratory specimens from patients with pneumonia were tested for Legionella by PCR.
During the 2-year period before the PCR testing strategy was introduced, there were 22 cases of legionnaires’ disease identified, compared with 92 cases after the PCR strategy was implemented. There were 1,834 samples tested after the strategy was implemented, and 1 in 20 specimens were positive. In the peak Legionella season (November to January), 1 in 9 specimens was positive.
“Routine and systematic use of PCR uncovered a large hidden burden of legionnaires’ disease in our region, and similar results will likely be found in other parts of the world,” Murdoch said. “Our approach will identify patients who have legionnaires’ disease so they can be treated with the right antibiotics, and clarify the importance of legionnaires’ disease in a region by providing a better picture of regional epidemiology.”
Murdoch said several efforts are now under way to identify potential methods to prevent legionnaires’ diseases, a “potentially preventable pneumonia.”
Disclosure: Murdoch reports no relevant financial disclosures.