In 2011, an independent review panel questioned if the opportunity for polio eradication was being squandered. It lit a fire under the movement. Partners increased their commitments. Frieden moved his effort into the CDC's Emergency Operations Center -- a high-tech amphitheater in which the disease is minutely tracked in maps and charts.
There are two regions where wild polio transmission has never been eradicated: in the tribal areas along the Afghanistan/Pakistan border and in northern Nigeria. In Afghanistan, efforts by the ministry of health have been innovative and successful. There have been only six cases so far this year, all of which (when the CDC examined the genetic fingerprints of the viruses) originated in Pakistan. In Pakistan, infections are largely confined to North Waziristan, where the local Taliban commander has banned vaccination. In Nigeria, the government has recently improved the management of its program and infections are down. But the terrorist group Boko Haram -- which rejects everything Western, including vaccines and education -- is suspected of being responsible for the murder earlier this year of nine polio workers. Polio is a killer that finds allies among killers.
Now a virus originating in Nigeria has caused an outbreak in Somalia, which has spread some cases to Kenya and Ethiopia. Health authorities in Mogadishu responded with surprisingly celerity, beginning immunizations four days after the first reported illness. But the problem persists in less populated areas controlled by al-Shabab. Somalia, which has ended polio transmission twice before, must do it a third time.
Polio eradication is an enterprise now conducted at the frontiers of medicine and war -- introducing vaccination into places that have never seen Western medicine and sometimes requiring negotiations with warlords and militias. In some places, the challenge is management; in others, security. The complexity can be frustrating. "It is like finishing a marathon," one CDC expert told me, "and being told you have an extra mile to run."
But these are struggles near the finish line of a landmark scientific achievement. And for those who doubt that any purpose of government can be essential, the daring, humane work of the CDC is a corrective.