This guide complains how and where to get 3 achievements of infected creature.
Locations of Infected Creature
First is in Chapter 2, Area 5
When you start, you can see the two waterfall. climb up and go right.
Second is in Chapter 3, Area 3
When you start, go to up.
And you can see ventilation hole.
Third is in Chapter 4, Area 3
During the 4-3, you can see this place. but you can not go in there. Just go right place.
Take the box to left place, and ride it.