PESHAWAR: Syed Wali desperately wants to immunise his three young children against polio but fears the militants who banned the vaccine from this remote area in northwest Pakistan will catch him if he tries to smuggle it in.

''I can afford to bring the vaccine for my children, but what answer will I give the Taliban if they recover the vaccine bag from my possession?'' Wali asked.

Wali's fears are shared by many in the North Waziristan tribal area as health authorities recently confirmed five new polio cases there and suspect there are many more.

It's one of a series of outbreaks this year in parts of the country where security threats have kept out vaccination teams.

Officials worry these outbreaks — inflamed by militant threats and attacks on vaccination teams — could worsen and spread to other parts of Pakistan, especially since the country is entering the high season for virus transmission.

''It's not like a pot of boiling water where you see bubbles coming from everywhere, but there is steam coming out from specific areas,'' said Dr Elias Durry, emergency coordinator for polio eradication in Pakistan for the World Health Organisation.

''Our fear is that the virus from these areas can go out and seriously jeopardise the success in fighting polio that has been achieved in the past couple of years.''

Pakistan — one of only three countries left where polio is endemic — had 198 confirmed cases in 2011, the highest number of any nation in the world. Pakistan was able to bring that number down to 58 in 2012 through a vaccination program that is supported by the United Nations.

But the militant threats could reverse that progress. There have been 27 confirmed polio cases in Pakistan so far this year — the third highest total in the world after Somalia and Nigeria. Seventeen of them have occurred in the country's semiautonomous tribal region, the main sanctuary for Taliban and Al Qaeda militants, Durry said.

Two powerful Pakistani Taliban militants have banned vaccinators from North and South Waziristan over roughly the past year because of their opposition to US drone strikes.

Gunmen have also killed over a dozen vaccination workers and police guards in different areas of the country. Many suspect the Taliban of carrying out the murders, although the group has denied the allegation.

Militants have claimed the vaccine is meant to sterilise Muslim children and have accused health workers of being US spies. The allegation gained traction after the CIA used a Pakistani doctor to try to confirm the presence of Osama bin Laden in 2011 under the guise of an immunisation program.

The threats have left residents like the shopkeeper Wali, who lives in the town of Miramshah, with the difficult decision of whether to defy the militants by smuggling the vaccine in for his children from Peshawar.

Some families couldn't afford to make the six-hour journey to get the vaccine from Peshawar, even if they wanted to take the risk.

Health workers have stationed themselves at two checkpoints protected by the army in North Waziristan, where they are vaccinating children riding by in vehicles. But many people are afraid the militants will find out if they vaccinate their children at the checkpoints.

The polio virus, which usually infects children in unsanitary conditions, attacks the nerves and can kill or paralyse. It can spread widely and unnoticed before it starts crippling children. On average, about one in 200 cases will result in paralysis.

Durry, the WHO official, said authorities have confirmed five polio cases in North Waziristan and three others in the nearby district of Bannu this year.

The five cases in North Waziristan were confirmed since the beginning of August, two of them on Wednesday, said a local health official, speaking on condition of anonymity because he was not authorised to talk to the media. Officials are still investigating 20 suspected cases, he said.

There have been a total of 12 confirmed cases since the militant ban, the official said.

Tribal elders sent to ask the militants to change their minds haven't been successful, said Jahan Mir, a senior government health official in Miramshah.

There also have been confirmed polio cases this year in the Khyber tribal area and the provinces of Khyber Pakhtunkhwa, Sindh and Punjab, Durry said.

Health officials had planned to immunise 34 million children across the country, but 1.5 million have not received the vaccine because of security threats, he said.