When struck by an infected while standing against a vehicle or building the the survivor's hit box remains locked to that infected's location. The infected will remain in the same spot and continue to attack even when the survivor has moved away from the infected. The survivor continues to take damage from the attack regardless of distance. The only solution I have found is logging out during the attack and logging back in. I have had this happen on three occasions, once beside a wrecked vehicle and twice against the outer wall of a building.

When being chased by an infected, run to and stand directly against a non movable structure such as a wrecked vehicle or building. Allow the infected to attack you then try to run away.

Moving away from the attack stops the survivor from taking further damage.