This year, Bern Halloway was the Head Gamemaker this year. Also, Velorum took interest in the medicine station and received skills and knowledge about it, and she trained in combat stations. These two skills she obtained would ultimately be the reason why she won, besides being in the Career pack.
The arena has all sorts of diseases and viruses on the air. The only way to cure yourself is to get medicine in the cornucopia. In the very center of the cornucopia, where the best supplies were, were hazmat suits that defended yourself from all viruses and diseases. Tributes that didn't participate in the bloodbath died from the infections since they didn't get anything to protect themselves.
The games lasted 5 days since some tributes decided not to enter the bloodbath, so they died in no time. They died after the bloodbath. That's how dangerous the infections were. You were in great danger if you had an open wound of course, and death would arrive quicker if you didn't act quick. Luckily the victor that year, Velorum, took interest in medicines during training and because of this, she survived the longest in the end. The non-career tributes that had supplies after the bloodbath didn't have much knowledge on how to treat themselves so 18 were dead on day 1. It's a little better from there since the remaining tributes knew about medicine and treated themselves. Velorum was packed with supplies, being with the careers and piggy packed them the whole time pretty much.