Polio is way down in Nigeria, in part because of Gates' first visit there early in 2009. A year and a half on, polio cases are nearly zero, just three so far in 2010 compared with 288 in the first half of 2009. Gates' arrival coincides with the first of two large-scale vaccination sweeps in Nigeria this month. Also, rather than directly fund polio vaccination efforts and hope for good results, the Gates Foundation agreed in 2009 to indirectly buy down existing World Bank loans to Nigeria when the country achieves specific vaccination targets. (See the picture Gates posted on Twitter which he entitled: "Reviewing statistics with leaders...")
Nigeria has 42 million children under 5; reaching 80% vaccination coverage takes an army of about 200,000 vaccinators. If polio can be dispatched in Nigeria, that would leave only India as a major polio epicenter, which Gates visited just three weeks ago. India also has seen its case rate fall precipitously but, unlike Nigeria, the oral polio vaccine doesn't always work even after repeated doses in the most polio-intensive regions of India. After Nigeria and India, the remaining polio redoubts are Aghanistan and Pakistan where vaccination campaigns are often impossible because of war-time conditions. Those are likely the only polio frontlines Gates won't visit.
Note on graphic: The location of the three cases reported so far in 2010 comes from AllAfrica.com. The map for 2009 is for illustrative purposes. It shows only half of 2009's cases with little fidelity to actual location.
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Related:
Polio Turns Stealthy in India (August 19, 2010)
Heavy Lifting: Raising Health Beyond Polio's Reach (May 13, 2010)
Wall Street Journal: Pulling the plug on polio eradication? (April 26, 2010)
Polio Eradication: Harder Than it Looks (April 14, 2010)