Why fungal invader Candida auris is learning to beat our heat

A wall that kept us safe

Your body heat is a protective shield. For millions of years, mammals kept their bodies warmer than the surrounding environment. Alongside adaptive immunity, our targeted defence system, this heat created a thermal barrier that stopped most cold-loving fungi from growing inside us.

Think of this barrier as a protective moat around a fortress. Most fungal invaders simply drowned in our high heat.

The moat is shrinking

Now, that shield is thinning from both sides. Fungi outside are adapting to rising heat driven by anthropogenic climate change, caused by human activity. At the same time, our own basal body temperature, our resting body heat, has steadily declined.

The ground outside the moat is rising, while the moat itself is drying up. The dangerous gap between our body heat and the environment is closing fast.

A tough new invader

Enter Candida auris. While its close relatives struggle at our body temperatures, this species is exceptionally thermotolerant. It thrives at 37°C and can survive all the way up to 47°C.

Because it can easily step over our internal heat wall, it causes severe, invasive infections with a mortality rate between 30% and 60%. Worse, it can stick to hospital surfaces and resist all three major classes of antifungal medicines.

It did not spread from a single outbreak either. Instead, genetically distinct clades, or ancestral branches, emerged independently on multiple continents. Shared pressures in our warming environment are nudging completely separate fungal groups toward the exact same threatening survival tactics.

What we still don't know

The review synthesises big ideas from evolutionary biology rather than running fresh laboratory experiments. Because of that, scientists still do not fully know the exact genetic mechanisms driving this high heat tolerance across every separate clade. We also cannot yet predict which wild fungal species will adapt next and cross our shrinking thermal moat.