In 2011, India, considered the most difficult place to achieve eradication, was declared polio-free.
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The shootings, in a series of attacks, represent a major setback in the quest for a polio-free world.
Infected travellers had carried the virus to nearly 20 previously polio-free countries causing more than 1200 polio cases.
For years, the Afghan Taliban leader, Mullah Omar, has been issuing safe-conduct letters to WHO-sponsored polio-vaccination teams operating in insurgent areas.
It will also risk the disease spreading beyond Pakistan's borders to India, which has been polio-free for more than a year.
Mazhar Nisar, a spokesman for the polio-monitoring cell at the Pakistani prime minister's secretariat in Islamabad, said the program wouldn't be suspended countrywide.
India has been polio-free for two years - a remarkable achievement.
Iraq has been polio-free for more than two years, and it is not likely that the cultures in the incubators contained wild poliovirus, according to the report.
In order to stop the spread of infections, health workers have to vaccinate nearly all children under the age of 5 multiple times a year in polio-affected countries.
She is a goodwill ambassador for Unicef, campaigning to fight polio - she contracted the disease when she was nine and one of her adopted children become paralysed after becoming infected.
Somewhere today, in Nigeria, a child is polio-free, a mother is nursing a healthy baby, a family is free of malaria because a business or a civil society group decided to devote attention and resources to their health.
The oral polio vaccine can - in very rare cases - trigger polio.
Then the repeated - sometimes monthly - polio immunisation rounds in at-risk communities can stop and the vaccine be part of the standard childhood schedule.
All I have is my past, but as I have been in counseling (up until two years ago, when it became physically impossible to do so.) to overcome my past-I endured three life threatening health diagnoses-polio, Hepatitis C, and breast cancer-as well as three abusive men-my first husband beat me unmercifully.
By the time these new details emerged, Polio was eighty-seven, and still living in Braintree.
Without widespread vaccination in those countries, polio could re-establish itself in any of them.
Now 80, he is largely confined to a wheelchair as a result of a post-polio syndrome.
Currently, the most accepted theory regarding the cause of post-polio syndrome rests on the idea of degenerating nerve cells.
Nobody knows exactly what causes the signs and symptoms of post-polio syndrome to appear so many years after the first episode of polio.
Correspondents say Sunni militants may have planted the mine - the upper Kurram area is dominated by Shias who do not oppose anti-polio efforts.
Jawad Ali, in charge of the anti-polio campaign in Kurram, told the AFP news agency that the pair had been killed "on the spot".
This collective resolve could not be more evident than in Pakistan, where the highest levels of government, local Muslim leaders and international partners are supporting the ongoing anti-polio effort.
But the fact is no acts of violence or intimidation, even as savage as the killings last week, stand a chance of derailing for any substantial amount of time the groundswell of willpower at the heart of the global anti-polio effort.
Over the past decade 15 billion doses of polio vaccine drops have been given and there have been 200 confirmed cases of circulating vaccine-derived polio virus.
This is a now or never moment - kick polio off the planet over the next few years or face a humiliating retreat which could see the virus re-emerge in scores of countries.
Hamid Jafari, project manager of the WHO-National Polio Surveillance Project (NPSP), has said this is the closest the world has come to global eradication of polio.
Polio is a vaccine-preventable disease that has been eradicated in most countries, but it still causes paralysis or death in some parts of the world, including Nigeria, Pakistan and Afghanistan.
And make no mistake about it: if measles, whooping cough, polio, and other vaccine-preventable diseases return, children will die.
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Polio is transmitted by faecal-oral contact, and a lot of this goes on in the crowded and unhygienic refugee camps around Luanda.
While delivering polio vaccinations, literally drop-by-drop, these brave volunteers and public health workers are helping build stronger health systems that engender trust and engagement at the community level.
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