With just a little more cash and a lot more political clout, polio could become the second dread disease to be wiped off the Earth, experts said on Tuesday.

The world effort to eradicate polio is short only $75 million. And leaders of the few countries where the virus is still endemic - Nigeria, Niger, Egypt, Afghanistan, India and Pakistan - need to get on board, they told a conference.

Tuesday was the 50th anniversary of the approval of the first vaccine against poliomyelitis, which once killed or paralyzed hundreds of thousands of children each year.

Caused by a highly infectious virus, polio usually causes common cold symptoms, but in a small percentage of people spreads to the digestive and nervous systems and can cause severe damage. Children under 5 are the most vulnerable.

Like smallpox, which was eradicated in 1979, polio infects only human beings. The vaccine works well and the World Health Organization believes polio could also be eradicated by the end of this year.

“We think that it is realistic to eradicate polio. The question is how fast we can eradicate polio,” said Dr. Robert Keegan of the U.S. Centers for Disease Control and Prevention.

“With some 200 countries polio-free, the feasibility to us is evident.”

Northern India, Pakistan and Nigeria pose the biggest problems, in part because of difficulty reaching the areas where the virus is still common, Keegan and colleagues told reporters in a telephone briefing.

“On a global scale you probably are looking at 400 million to 500 million children at particularly high risk that we need to hit over and over again to eradicate polio this year,” Keegan said.

“The total cost is over $600 million but the shortfall is $75 million.”

A 15-year effort called the Global Polio Eradication Initiative, involving more than 200 countries, 20 million volunteers and $3 billion, succeeded in driving the number of polio cases worldwide from 350,000 in 1988 to fewer than 700 cases in 2003.

This popped back to nearly 1,185 in 2004, largely because of the continuing spread in Nigeria. From Nigeria polio has now spread to more than a dozen neighboring countries.

Dr. David Heymann, head of the WHO’s polio eradication program, said the biggest obstacle was “political engagement.” “If a president or prime minister wants the job done, it can be done,” he said.

“That will occur in India, that will occur in Nigeria,” he added.

Until then, every child in the world will need a series of polio shots.

“The number of children that need to be vaccinated in the world remains the number of children in the world, because polio still exists in the world,” Heymann said.