In the video, you'll see a cricket jump into a pool, and then after it has drowned, a long worm will swim out of its carcass.

The gordian worm is a nifty creature: it's a parasite, and when it enters its host, it can take over nervous and muscle tissues. While inside the host, it steals nutrients, then when it's had its share, it makes the host kill itself, and the gordian worm leaves the body to look for yet another host.

I don't believe it has the power to do this to the large and complex human system, so no need to worry about suicidal zombies... YET.