Destroy 25 Infected Water Towers before they hatch.

Near infected zones you will see average looking Water Towers. You are shown these in an early mission. However, when you get close to these towers, they appear infected. You must destroy the tower within 5 seconds of getting too close to it before it hatches and you have a Hunter on your ass. The easiest way that I've found is to use the Whipfist from a distance, so it doesn't hatch, or use the arm blade and slice away quickly. Infected Towers are easily spotted by crows circling them ahead and they are only found in the red zones.