Polio could be eradicated in Pakistan within months, health officials say, as a mass vaccination drive is launched.
A World Health Organization spokesman told the BBC only a handful of cases have been reported this year in Pakistan and neighboring Afghanistan.
The two countries are the last places where polio remains endemic.
It is hoped millions of children will be vaccinated over three days. Police escorts will guard against Islamist militants who oppose immunizations.
“The challenges we have are both logistics and security,” the WHO’s representative for Pakistan, Dr Michel Thieren, told the BBC.
He said about 70,000 medical staff aimed to immunize almost 10 million children in the drive, which is taking place in Khyber Pakhtunkhwa and semi-autonomous tribal areas in the north-west, as well as in southwest Balochistan Province.
“They have with them 12 million doses for the coming three days,” he said.
“We are very close. A handful of cases [were] noticed this year - about 11 in Pakistan and I think about five in Afghanistan.
“This is the lowest toll of cases in history. We expect to be within months of polio elimination in Pakistan.”
The WHO’s optimism comes after the Pakistani authorities launched repeated anti-polio drives in high-risk areas.
Health teams gained access to formerly hostile regions in the northwest after the Pakistani military launched a 2014 offensive against the Taliban in North Waziristan.
Attacks on health workers have dropped since then, although they still remain a threat.
Islamist militants oppose vaccination, saying it is a Western conspiracy to sterilize Pakistani children.
In April seven policemen, three guarding polio workers, were killed in Karachi. A January bomb attack on a vaccination centre in Quetta killed 15 people.
Pakistan recorded more than 300 polio cases in 2014, its highest number since 1999. The number of cases fell to 52 last year.
In 2015, polio was endemic in only two countries - Pakistan and Afghanistan.
