Family members of Nasima Bibi, a female worker of an anti-polio drive campaign who was shot by gunmen, mourn at a hospital morgue in Karachi on Dec. 18.

Pakistani rescue workers carry the dead body of a female polio worker, killed by unknown gunmen, at the morgue of local hospital in Karachi, Pakistan, on Dec. 18. Gunmen killed several people working on a government polio vaccination campaign in two different Pakistani cities on Tuesday, officials said. The attacks were likely an attempt by the Taliban to counter an initiative the militant group has long opposed.

A Pakistani health worker marks an infant after immunization with anti-polio drops in Lahore, Pakistan on March 12. Pakistani officials vow to eradicate polio by the end of 2012. Polio remains endemic in four countries – Afghanistan, India, Nigeria and Pakistan.

Residents living in the suburbs of Lahore, Pakistan carry their children to have polio drops administered to them on Monday, March 12. Pakistani officials vow to eradicate polio by the end of 2012. Polio remains endemic in four countries – Afghanistan, India, Nigeria and Pakistan

A woman holds her child as she waits for a polio vaccination in Peshawar, Pakistan, on March 12. Reports state that polio cases over last month has taken the country's total number of poliomyelitis-affected children to five in 2012, officials said. Most of the 198 cases recorded in 2011 were notified in the north western part of the country where local religious clerics and pro-Taliban lobby are reportedly trying to convince residents that the US-manufactured polio drops were designed to sterilize Pakistanis and reduce the Muslim population.

A health worker administers a polio drop to a newborn baby at Chacha Nehru Bal Chikitsalaya in New Delhi, India, on Jan. 13, 2012. India is marking a full year since its last reported case of polio on Friday. The milestone is seen as a major victory in the global effort to eradicate the crippling disease.

A polio patient wipes himself after a bath at a government home for the disabled in Hyderabad, India on Jan. 12, 2012.

Polio vaccination team members update their records after administering polio drops to a child, center, on the outskirts of Ghaziabad in the Indian state of Uttar Pradesh on Jan. 25.

A boy receives anti-polio vaccination drops from a health worker as part of a polio vaccination campaign in Amritsar, India on Jan. 23. Polio is a pandemic threat in four countries, namely India, Afghanistan, Pakistan and Nigeria, compared to 125 countries in 1988. There were 1,606 cases of polio in 2009, down from about 350,000 in 1988.