Rescue workers at a hospital morgue in Karachi, Pakistan, carry the body of a female polio worker killed by unknown gunmen on Tuesday, Dec. 18, 2012. (AP Photo/Fareed Khan)

Photo by: Fareed Khan

Rescue workers at a hospital morgue in Karachi, Pakistan, carry the body of a female polio worker killed by unknown gunmen on Tuesday, Dec. 18, 2012. (AP Photo/Fareed Khan)