A U.S. survey of polio cases in Nigeria shows the number of people infected with the crippling illness is starting to drop after a period of resurgence. Public health officials say progress in polio eradication is the result of an intensive control effort.
Children are the ones most affected by polio which, at its worst, can leave their legs shrunken and floppy, making it impossible for them to walk.
Experts say about one in 200 children develop this paralytic form of the disease. While the numbers do not seem high, the polio virus is highly infectious and it can spread widely in places where vaccination is spotty.
Fears about the vaccine's safety three years ago prompted some northern Nigerian states to suspend mass vaccination. Soon, there was a polio resurgence in Africa's most populous country, and the disease spread to 18 countries that had been polio free for more than one year.
But a new survey by the U.S. Centers for Disease Control and Prevention in Atlanta, Georgia finds that renewed polio immunization efforts throughout Nigeria have resulted in the roll-back of the crippling disease.
According to the survey, which calculated cases of polio in the region over several months last year and this year, the number of confirmed polio cases fell from 574 in 2004 to 377 this year.
Steven Wassilak of the U.S. Centers for Disease Control and Prevention in Atlanta credits renewed mass vaccination campaigns by state and local authorities in Nigeria.
Dr. Wassilak, a medical epidemiologist with the global immunization program at the Centers for Disease Control, says the data once more show polio control efforts must include government education campaigns and routine childhood vaccinations.
He says population studies such as the CDC report, by showing where the disease has spread, also play a role in preventing it from spreading further.
"The real big effort then is tracking the disease better, doing better surveillance, and using the laboratory data from that surveillance to pinpoint better where the disease is occurring and trying to approach those areas better. And then we are doing the campaigns, we're really taking efforts to reach every child by going house to house," Dr. Wassilak says.
Dr. Wassilak says the effects of Nigeria's polio resurgence are still reverberating in other countries, with new cases showing up in Eritrea and Indonesia. But he says the Nigerian survey provides fresh evidence that standard polio control methods involving mass immunization and education are effective.