In a telephone interview with Reuters, Gates was optimistic about the global plan to eradicate the paralysing viral disease, but said Afghanistan’s conflict and power struggles hamper progress. “The big issue there is always with the Taliban,” said Gates, whose multi-billion dollar philanthropic Bill and Melinda Gates Foundation is one of the biggest funders of the polio eradication campaign. Polio is a virus that spreads in areas with poor sanitation. It attacks the nervous system and can cause irreversible paralysis within hours of infection. Children under five are the most vulnerable, but polio can be prevented with vaccination.