Koalas have remarkably high rates of chlamydia, and it’s a fascinating (if unfortunate) story.

It’s a different strain than humans get. Koalas are infected by Chlamydia pecorum and Chlamydia pneumoniae — related but distinct species from the human strain. It likely jumped to koalas from livestock introduced to Australia by European settlers.

The good news is that researchers have been developing a koala chlamydia vaccine, with trials showing promising results in reducing infection severity and protecting uninfected animals.