Cryptococcus gattii as an important fungal pathogen of western North America

Cryptococcus gattii, a pathogenic fungus historically appreciated to be endemic to tropical regions, was recognized to emerge in a more temperate zone of North America in the 1990s. Early reports focused on an outbreak that was first apparent on Vancouver Island (BC, Canada), involving both the veterinary and human population. More recently, it has been recognized that this organism is endemic to a wider geography in western North America, with recognized disease caused by unique molecular subtypes in both healthy and immunosuppressed human hosts and a variety of domestic and wild animals. A number of cases of disease caused by C. gattii isolates that are unrelated to the Vancouver Island-Pacific Northwest outbreak strains have also been recognized in different parts of the USA. As microbiology laboratories have historically not identified these organisms to the species level, our current understanding of the scope of this infection is probably an underestimate. Ongoing public health epidemiologic efforts will be facilitated by increased attention towards culture-confirmed diagnosis and species identification in clinical microbiology laboratories. Early experience presents a strong rationale for increasing diagnostic attention, with multiple clinical features that are unique to this infection, including variability in antifungal susceptibilities and a heightened need for aggressive management of inflammatory responses. Larger prospective studies to evaluate and optimize clinical management are needed.