My first impression was that the food drop had been there for quite a while... and they had never seen it, even though it seemed to be on along a regular route. Just checking again for clues.. cant see any but if it is recently dropped then all the growth around it would be rather disturbed. Obv there wud be a noticable gap in the trees above it, but theres no view of that in either the episode or the promo for dave.

I like begrowwa's theory that their could be vaccination within the dharma food. (Even though it would be rather expensive and time consuming to do). Its been a while since they all had a bit of dharma nutrition and now its time again. At least we know Hurley would be nice and immune... Survival of the 'fittest'?