The world's success in eradicating polio now depends on four countries - Afghanistan, India, Nigeria, and Pakistan - according to the Advisory Committee on Polio Eradication (ACPE), the independent oversight body of the eradication effort.
With a targeted vaccine and faster ways of tracking the virus, most countries that recently suffered outbreaks are again polio-free.
In parts of the four endemic countries, however, there is a persistent failure to vaccinate all children, and polio-free countries are considering new measures to help protect themselves from future outbreaks.
"With a more effective monovalent vaccine and accelerated lab processes for identifying poliovirus, these countries have the best tools we've ever had," noted Dr Stephen Cochi, Chair of the ACPE and Senior Adviser to the Director of the Global Immunisation Division at the US Centers for Disease Control and Prevention.
"Eradicating polio is no longer a technical issue alone. Success is now more a question of the political will to ensure effective administration at all levels so that all children get vaccine."
Steve Cochi, chair of an advisory panel that oversees international efforts to eliminate the disease, faulted the last four countries where polio is endemic for failing to ensure children receive the cheap oral vaccine that stops its spread.
"Polio continues in these few areas ... because authorities are persistently failing to reach every child," Cochi, a senior adviser on global immunisations at the US Centers for Disease Control and Prevention (CDC), told a news briefing.
As an illustration, the office of Afghan President Hamid Karzai has already taken direct oversight of polio vaccinations, following the sharp increase in cases in the Southern Region of Afghanistan.
Given that all children paralysed by polio in the world this year were infected by virus originating in one of the four endemic countries, polio-free countries are now taking new measures to protect themselves.
The Ministry of Health of Saudi Arabia, for example, will be enforcing stringent polio immunisation requirements for the upcoming pilgrimage to the holy city of Mecca.
"Polio eradication hinges on vaccine supply, community acceptance, funding and political will. The first three are in place. The last will make the difference," said Dr Robert Scott, Chair of Rotary International's PolioPlus Committee, speaking on behalf of the spearheading partners of the Global Polio Eradication Initiative.
Rotary is the top private-sector contributor and volunteer arm of the Initiative, having contributed US $600 million and countless volunteer hours in the field since 1985.
The ACPE advised the four polio-endemic countries to set realistic target dates for stopping transmission, noting that improvements in reaching all children in these areas have been only incremental, and that these countries will take more than 12 months to end polio.