Actually in yu113.doc there is a story about Yukkuri influenza.
104. Anon is returning home from work, dressed in a factory worker's coat so that yukkuris stay away from him. One Yukkureimu, however, bumps into him and screams some unintelligible things about him taking it in exchange for its children. He takes it home, and it eventually explains that its children can't take it easy, so it was planning to give itself to a factory worker in exchange for help from them. Anon is not from the factory, but he's touched, so they go to their nest to see what's wrong. He finds that the koyukkuris are abnormally warm, and recalls that Eirin had said that yukkuri illnesses exist as well, and the yukkurienza is a particularily dangerous one. He takes them all home, and tells the mother to gather a lot of food for them. (Until now, they mostly threw it up.) Anon notes that the eldest sister isn't too badly affected, and it turns out that it had been through the disease when it was young. Anon tells the mother that inside the eldest, there's a medicine that can cure the others. The mother protests, but the eldest offers itself for its siblings. Anon scoops out some of its bean paste (it somehow tolerates the pain), and feeds it to the others. After a few days of repeating this, one of the koyukkuris is finally able to take it easy. The mother and the eldest are ecstatic. They keep up the treatment until all of them are okay. After this, however, the mother succumbs. The children are saddened, but afterwards, some decide to leave on their own, and some decide to stay with Anon, including the eldest, which says "If any other yukkuris get sick, use my bean paste to help them." Anon is now selling medicine for yukkurienza.