A fungus appeared on three continents at once

Each outbreak carried a different genetic fingerprint, which ruled out a single outbreak spreading around the world. Researchers at Johns Hopkins proposed an explanation that had nothing to do with hospitals passing the fungus between patients.

Arturo Casadevall's team at Johns Hopkins argued that most fungi cannot survive at human body temperature, which is why so few cause serious disease in people. A warming climate, they proposed, had pushed environmental strains of the fungus just past that thermal barrier, turning a harmless environmental organism into a human pathogen in several places at once.

The hypothesis is still unproven, and the authors are careful to say other factors, like global antifungal use in farming, could also explain the pattern. But Candida auris has kept spreading since 2019, now resistant to multiple antifungal drugs in some hospitals, and a 2021 study by other researchers found it in remote coastal wetlands in India, consistent with an environmental origin.

A heat-tolerant fungus, with a warmer world as suspect.