In 2009, C. auris was discovered for the first time in a Japanese inpatient. The pathogen was classified as an urgent threat by the Centers for Disease Control and Prevention (CDC) in the United States (US). In addition, the World Health Organization (WHO) listed C. auris as a fungal pathogenic species of critical concern in their list of fungi to be prioritized in October 2022.
This fungus independently and concurrently evolved into five clonally distinct clades on three continents. 47 isolates were subjected to whole-genome sequencing, which revealed numerous single nucleotide polymorphisms (SNPs) and low intra-regional genetic diversity, pointing to a nearly contemporaneous emergence in various geographical locations.
Hypothetical emergence due to global warming
Global warming is proposed as the likely explanation for the independent and contemporary emergence of distinct C. auris clades. Few fungal species are pathogenic in endothermal animals and humans; very few fungi thrive at mammals’ high basal temperatures, creating a thermal barrier preventing infections.
Several reports suggest that increasing environmental temperatures due to climate change may result in the selection of thermotolerant fungal lineages that can circumvent the thermal barrier and infect/colonize endothermic animals.
One study showed that C. auris could grow at elevated temperatures than its close phylogenetic relatives. In addition, the remarkable halotolerance exhibited by this fungus suggested that it could have previously existed as an environmental species in wetlands/marshes.