04/30/2015 12:30 EDT | Updated 08/08/2015 08:59 EDT

Campaign to wipe out polio has never been in such a strong position: UNICEF

TORONTO - The nearly three-decades-long battle to wipe out polio is making significant progress and may be poised for success, leaders in the campaign said Thursday.

"Our consensus in the polio community is that we've never been in a better place to hold hopes of being able to eradicate this disease once and for all," said Peter Crowley, UNICEF's head of polio, during a media briefing on the state of the program.

Crowley and others quickly noted, though, that it is too soon to declare victory. All who have worked on the polio program know that with this wily virus, complacency is a dangerous state of mind. Too often gains have been followed by devastating setbacks.

To date this year there have only been 23 cases of polio recorded, in only two countries — Pakistan and Afghanistan. Last year at this time there had been 68 cases spread over eight countries.

Adding to the optimism is the fact that Nigeria has not reported a single case in more than eight months. Africa's most populace country is one of three remaining countries where polio is considered endemic, meaning spread there has never been completely snuffed out.

Viruses from the endemic countries sometimes spill over into neighbouring nations — sometimes even countries far afield — and ignite outbreaks.

If Nigeria goes 12 months without a case, it will come off the endemic countries list, leaving only Afghanistan and Pakistan as places where polio viruses are spreading.

A further indication that transmission may have stopped in Nigeria is the fact that the country has not found wild polio viruses in the sewage surveillance system it operates. People infected with polio shed viruses in their stool; a number of countries test sewage for polio viruses as a way to enhance surveillance.

"We have never gone anywhere near this long without any wild polio virus isolated from either Nigeria or of course Africa," said Jay Wenger, director of the polio program for the Bill and Melinda Gates Foundation, one of the partners in the eradication effort.

To date smallpox is the only human disease that has ever been eradicated. Buoyed by the success of that program, four partners embarked on a bid to rid the world of crippling polio in 1988. Their goal was to complete the task by the year 2000.

The four original partners were the World Health Organization, UNICEF, the U.S. Centers for Disease Control and the service club Rotary International. The Gates Foundation joined the fight later on.

Wenger acknowledged the Boko Haram insurgency in northern Nigeria is creating problems by limiting access to some children who require vaccination.

But he said surveillance programs that look for cases of paralysis in children are still operating. Polio program leaders are "reasonably confident" the virus isn't spreading in Nigeria, Wenger said, though he cautioned "we clearly are not out of the woods there."

There have also been improvements in Pakistan, where violence against polio vaccination teams in some parts of the country has bedevilled the efforts there. There have been all too frequent killings of vaccination teams — and the police escorts assigned to keep them safe — by supporters of the Taliban, which has opposed polio vaccination in Pakistan.

Aziz Memon, the chair for Rotary's PolioPlus committee in Pakistan, said renewed efforts to secure the safety of vaccination teams appear to be working.

The current target for extinguishing polio is the end of this year.