- In "274", it's revealed that one of the base's other labs has been testing an anti-viral agent against every known virus, including smallpox: the one human disease which has been driven completely extinct, save a handful of laboratory samples. The revelation that the base has such samples is scary enough ... but to test a cure for smallpox, they'd presumably have to infect some research subjects and see if the cure helped them. Smallpox was exclusively a human disease; it can't infect other animals. So if they really tested their cure on smallpox, they had to have used human test subjects ... and the cure, itself, kills 75% of those treated with it.
- Though that well may be what really happened given Hatake's evasiveness and Balleseros' suspicions, That Other Wiki does mention other animals, (like primates) have been infected in lab settings.
Fridge / Helix