Two Cases of Legionnaires’ disease following exposure to a hot tub at a private residence – Ontario, 2021

On September 10, 2021, the Haliburton, Kawartha, Pine Ridge District Health Unit in Ontario, Canada, received a case report of Legionella pneumophila serogroup 1 in a patient (case 1) hospitalized for pneumonia. A second case (case 2) within the same household was also identified. Case 1 was laboratory diagnosed by urine antigen testing, whereas case 2 was diagnosed by PCR and culture from a respiratory specimen collected from case 2, both at Public Health Ontario Laboratory, Ontario, Canada. Cases were linked by household and both cases were exposed via a newly purchased but previously used hot tub. Samples from the hot tub were culture positive when tested at PHO’s Laboratory. Given a respiratory culture isolate was available, together with an environmental isolate from the hot tub, sequence based typing was undertaken. Having both a clinical and an environmental culture isolate is essential for molecular investigations. The sequence type for the clinical isolate was the same as the environmental isolate, providing additional evidence that the hot tub was the source of infection for both cases.