Priest PC, et al. - Given the underdiagnosis of legionnaires' disease due to inconsistent use of diagnostic tests and a lack of certainty about whom to test, researchers examined the rate of case detection after large-scale introduction of routine PCR testing of respiratory specimens in New Zealand. Over 1-year, LegiNZ, a national surveillance study, was conducted to maximize the identification of cases of Legionnaires' disease in hospitals via active case-finding. They routinely tested respiratory specimens from patients of any age with pneumonia, who could provide an eligible lower respiratory specimen, admitted to one of 20 participating hospitals, covering a catchment area of 96% of New Zealand's population, for legionella by PCR. Via mandatory notification, they identified additional cases of Legionnaires' disease in hospital. During the study period, the rate of notified disease was three-times the average over the previous 3 years. They gained better clarification of the regional epidemiology of Legionnaires' disease and uncovered a hidden burden of disease performing active case-finding through systematic PCR testing. These data seem valuable for informing local Legionnaires' disease testing strategies, enabling targeted antibiotic therapy, and the identification of outbreaks and effective prevention strategies.