In the first episode that delves into the development of The Last of Us, the Hush are the center of attention; from the beginning of the initial concept to their design.
The Hush is a relatively recent enemy revealed in The Last of Us that Joel and Ellie will have to deal with throughout their travels. This particular type of infected uses a form of echo-location to find its way around and track other living things. I believe they’re also instant kills, so taking them on from a distance or sneaking around them are your only two options.
The Last of Us is set to release on June 14th.