Good old zombie ants. All you need to do is find somewhere for the zombies to need to go, and maybe give the fungus some kind of intelligence (it can't make the zombies run because it doesn't have *that* good control over its hosts), so that it can work out when it needs to attack stuff. At which point, a human needs food to provide energy for travel/fighting, so why not eat what you just killed? They could potentially have a slightly higher strength from not being limited by pain, and along the same lines, would not be knocked unconscious under the usual circumstances. Sufficient antibiotics will cure the infection, but good luck giving someone antibiotics before they gnaw your arm off.
That would, incidentally, allow for a resolution other than simply escaping; get as high a dose of antibiotics into the air as possible; they breath it in, and are cured - as are any minor infections. Obviously, anyone with a massive fungus growing out of their head is still dead, but you can't have everything...