A tiger in Tennessee became ill with a serious fungal infection caused by a lesser-known fungus called Blastomyces gilchristii. While blastomycosis is typically caused by a different fungus species, this case represents the first detection of this particular cryptic fungal species in the southeastern United States. Scientists used advanced genetic sequencing to identify the fungus when standard laboratory methods failed. This discovery suggests that this dangerous fungus is spreading to areas where it was not previously thought to exist.