User blog comment:Mckrongs/Monster Hunter 4 for the Nintendo 3DS/@comment-86.171.224.79-20121215222424/@comment-83.165.23.90-20121216104801

^ So... that explains why Tigrex gets in "infected mode" when it was near death, and in this mode, it looks more agressive.

Anyway, sometimes when a monster is near death it doesn't limp, because it has no time to scape. So isn't totally confirmed that the virus gives an special mode near death or revives monster's corpses.