Millicron

Millicrons are a species of sapient airborne microorganisms which can infect human bodies causing a severe fever. Despite being a pathogen for Humans, the Millicrons are actually civilized creatures, the disease they cause being unintentional (making them similar to the Xchagger plague). Therefore when one is infected with them it is necessary to seek out a treatment that wouldn't involve genocide (such as using antibiotics). Instead, the Millicrons must be carefully evacuated from the host.