We conducted a retrospective descriptive analysis of deidentified clinical and public health data from Nova Scotia Health to identify C. gattii cases from January 1, 2016–December 31, 2024. Because C. gattii was not provincially notifiable during the study period, we ascertained cases retrospectively through laboratory and clinical records; infectious diseases physicians assisted in case identification and clinical interpretation. We classified 6 cases as confirmed C. gattii according to Nova Scotia Communicable Disease Surveillance Guidelines (9).

Initial diagnostic testing reported for the cases included routine fungal culture using sheep blood and inhibitory mold agar of clinical specimens and cryptococcal antigen testing of serum or cerebrospinal fluid. We identified species of cultured isolates by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. C. gattii isolates were referred to the British Columbia Centre for Disease Control Public Health Laboratory (Vancouver, BC, British Columbia) for molecular typing by multilocus sequence typing. We interpreted test results according to the Nova Scotia Communicable Diseases Manual (10). Three additional cryptococcal antigen–positive cases did not meet the confirmed C. gattii case definition because species-level identification was unavailable; we therefore excluded them from the analysis.

We obtained demographic information, clinical characteristics including initial symptoms, and reported exposures through chart review, case investigation, and public health nurse–led interviews (Table) and documented the data in Nova Scotia’s Public Health surveillance system. Infectious diseases physicians supported case identification and clinical interpretation. We obtained verbal consent for interviews. Data were collected during January–February 2025, and final extraction was completed March 11, 2025.

Figure

Figure. Number of confirmed Cryptococcus gattii infections by year of diagnosis, Nova Scotia, Canada, 2016–2024.

We identified 6 species-confirmed C. gattii infections that were reported during 2016–2024 (Figure). Five cases occurred in the Western Zone and 1 in the Eastern Zone of Nova Scotia. All 5 Western Zone isolates were VGIIb; 4 case-patients reported no travel outside Nova Scotia, whereas 1 reported travel to British Columbia. The Eastern Zone isolate was VGI. That case-patient had previously resided in South Africa, where VGI has been identified through national laboratory surveillance (11); therefore, the geographic source of acquisition was uncertain.

All 6 case-patients had clinical syndromes involving the CNS; 2 also had pulmonary involvement. Five case-patients were presumed immunocompetent, and 1 was immunocompromised. All 6 case-patients were hospitalized; 1 required intensive care, and 1 died. Because information on smoking, vaping, sharing of smoking or vaping devices, and outdoor and occupational exposures were obtained retrospectively, that information was incomplete for some cases.

The concentration of VGIIb C. gattii infections in western Nova Scotia, including 4 cases in persons without travel outside the province, together with previous detection of a VGIIb-like strain in a free-ranging white-tailed deer in the region, supports local acquisition and suggests possible environmental persistence (8). The clinical findings demonstrate potentially severe disease: all confirmed cases had clinical syndromes involving the CNS, 1 patient required intensive care, and 1 died. Five of 6 case-patients were presumed immunocompetent, reinforcing the importance of considering C. gattii in compatible CNS manifestations regardless of recognized immune compromise. The small number of cases and incomplete exposure ascertainment precluded conclusions regarding smoking, vaping, sharing of smoking or vaping devices, occupational exposures, or specific environmental exposures as risk factors, although all cases included reported regular outdoor activities. Targeted environmental and One Health investigations are needed to characterize potential reservoirs and exposure information, and potential recall bias.

This analysis was limited by the small number of cases, retrospective design, incomplete clinical and exposure information, and potential recall bias. Because C. gattii was not notifiable during the study period, infections might have been missed. Three additional cryptococcal infections lacked species-level confirmation and were therefore excluded from analyses supporting genotype distribution and local acquisition. Environmental sampling was not conducted, precluding direct confirmation of a local reservoir. Differences in surveillance, diagnostic practices, and case ascertainment also limit comparisons with established endemic regions such as British Columbia (12).

In summary, addition of C. gattii to cryptococcosis in Nova Scotia’s notifiable disease list in 2026 provides an opportunity to improve case ascertainment, standardized investigation, and laboratory characterization. Integrated human, animal, and environmental surveillance could better define the geographic distribution, environmental reservoirs, and ecology of C. gattii in Atlantic Canada.