The Bill & Melinda Gates Foundation announced Monday that it would give $100 million to Rotary International's efforts to eradicate polio worldwide. It is the foundation's largest such grant.
Rotary said it would match the grant.
"We have very few opportunities to improve the world's public health in a permanent way, and this is one," said Dr. Margaret Chan, director general of the World Health Organization, which leads the eradication campaign in coordination with UNICEF, the U.S. Centers for Disease Control and Prevention, and Rotary, a worldwide volunteer group.
"We are closer to this goal than ever before. All four of the remaining polio-endemic countries are largely on track to reach very ambitious milestones," Chan said, referring to India, Nigeria, Pakistan and Afghanistan.
William H. Gates Sr., co-chairman of the foundation, said he hoped the grant would spur others to contribute.
Polio, which can cause paralysis and death, is spread person-to-person or through contaminated water. Since the eradication campaign began in 1988, the number of annual cases has fallen by more than 99%; 735 cases have been detected this year through Nov. 20, including new outbreaks in seven nations that previously had eliminated the disease.
Immunizing every child -- particularly in the conflict zones of Afghanistan and Pakistan -- presents a formidable challenge. Part of the problem, said Dr. Bruce Aylward, who directs the eradication effort, is that for each case of paralysis, about 200 asymptomatic -- and often undetected -- infections take place. Asymptomatic individuals remain healthy but spread the polio virus.