Cryptococcus gattii in the United States: clinical aspects of infection with an emerging pathogen

Abstract

Background: Cryptococcus gattii (Cg) has caused increasing infections in the US Pacific Northwest (PNW) since 2004. We describe this outbreak and compare clinical aspects of infection in the United States among patients infected with different Cg genotypes.

Methods: Beginning in 2005, PNW state health departments conducted retrospective and prospective passive surveillance for Cg infections, including patient interviews and chart reviews; clinical isolates were genotyped at the US Centers for Disease Control and Prevention (CDC). We examined symptom frequency and underlying conditions in US patients with Cg infection and modeled factors associated with death.

Results: From 1 December 2004 to July 2011, 96 Cg infections were reported to the CDC. Eighty-three were in patients in or travelers to the PNW, 78 of which were genotypes VGIIa, VGIIb, or VGIIc (outbreak strains). Eighteen patients in and outside the PNW had other molecular type Cg infections (nonoutbreak strains). Patients with outbreak strain infections were more likely than those with nonoutbreak-strain infections to have preexisting conditions (86% vs 31%, respectively; P < .0001) and respiratory symptoms (75% vs 36%, respectively; P = .03) and less likely to have central nervous system (CNS) symptoms (37% vs 90%, respectively; P = .008). Preexisting conditions were associated with increased pneumonia risk and decreased risk of meningitis and CNS symptoms. Nineteen (33%) of 57 patients died. Past-year oral steroid use increased odds of death in multivariate analysis (P = .05).

Conclusions: Clinical differences may exist between outbreak-strain (VGIIa, VGIIb, and VGIIc) and nonoutbreak-strain Cg infections in the United States. Clinicians should have a low threshold for testing for Cg, particularly among patients with recent travel to the PNW.