Altaf Qadri, Associated Press
In this Sunday Jan. 23, 2011 photograph, Sanjana Shoba, a polio vaccinator, administers polio vaccine to a child in Tilkeshwar village, some 200 kilometers from Patna, India. India will celebrate a full year since its last reported case of polio on Friday Jan. 13, 2012, a major victory in a global eradication effort that appeared to be stalled just a few years ago.

MUMBAI, India — A Bill Gates-backed effort to wipe out polio got a welcome boost after India, one of the last strongholds for the crippling disease, found no case for a year.

The anniversary Friday of India's last reported polio infection marks the longest time that transmission has stopped in the country which had the most cases in the world in 2009. India's success shows eliminating the disease is possible where there is "political will, quality immunization campaigns and an entire nation's determination," Gates, 56, chairman and co-founder of Microsoft, said in a statement.

India will be declared free of polio if it goes two more years without cases. Stopping the virus in the nation, one of four where transmission has never been interrupted, is crucial to ridding the world of a germ that paralyzed more than 350,000 children in at least 125 countries annually before a global effort to fight it began 23 years ago.

"Just a few years ago, doom mongers said that polio could not be stopped in India," said Liam Donaldson, England's former chief medical officer, who chairs a panel monitoring eradication efforts. "This week's milestone should provide a real boost for those countries still struggling to stop polio."

India, where more than 65 percent of people lack a toilet and 500,000 children die each year from diarrheal illnesses, has had the world's "most tenacious reservoir" of poliovirus, according to Margaret Chan, director-general of the World Health Organization. The country's last reported case was on Jan. 13, 2011, in the state of West Bengal.

Poliovirus is shed by infected people in feces and can spread as a result of poor sanitation and hygiene. Millions of people were paralyzed by the disease in the 20th century before vaccines became widely available in the 1950s. Sanitation improvements and routine immunization have helped eradicate the disease from all but 14 countries in Asia and Africa.

"India has exported polio in the last two decades to pretty much every place in the world," Deepak Kapur, who chairs Rotary International's polio committee in India, said in an interview. "The virus can come back via the same route."

The Global Polio Eradication Initiative, formed by the WHO, the United Nations Children's Fund, Rotary International and the Centers for Disease Control and Prevention in 1988, wants India's success to counter a decline in funding.

"We must ensure that India's polio program continues to move full-steam ahead until eradication is achieved," Gates said. Raising funds can "ultimately save billions of dollars and help to ensure that no child ever suffers from this crippling disease again."

The billionaire, who contributes about $150 million annually to the cause through the Bill & Melinda Gates Foundation, last year made polio eradication the foundation's top priority.

A $410 million financing gap threatens to undermine eradication efforts amid a spike in outbreaks in nearby Pakistan, which reported a third of the 620 cases found worldwide in the past year.

Floods that inundated parts of southern Pakistan in August frustrated efforts to immunize children in remote villages, said Mazhar Ali Khamisani, an official with the Sindh provincial government overseeing polio immunizations.

"The majority of the cases erupted in the flooded areas and then people carried the infection elsewhere," he said, adding that fighting between government and pro-Taliban forces in Pakistan's Khyber region also prevented access.

"Without urgent and fundamental change, it is a safe bet that it will be the last country on earth to host polio," the International Monitoring Board of the Global Polio Eradication Initiative, the group chaired by Donaldson, said in October.

The cross-border movement of people into northern India risks reintroducing the virus there, said Tim Petersen, a polio officer with the Gates Foundation in Seattle.

"Everybody needs to be on a heightened state of alert," he said. "The community and government cannot afford to get complacent."

Officials at checkpoints close to the Pakistan border are routinely assessing travelers for paralysis and other polio symptoms and children younger than 5 years are compulsorily vaccinated, said Balwinder Singh, a polio project officer who oversees immunizations in Punjab state's health department.

"The threat of an infected person crossing over is very real," he said over the telephone from Chandigarh. "There are polio pockets very close to the border."

Anis reported from Karachi, Pakistan.