Despite a growing polio epidemic in Africa, health ministers from the most seriously affected countries say they can stop its spread by the end of this year by intensifying efforts to immunize tens of millions of children.
At a meeting of the WHO in Geneva on Thursday, the ministers said they expected to repeat the success of large-scale immunization programs that nearly eliminated polio from Africa by 2003.
But last year, the number of African children paralyzed by polio more than doubled, to 1,037 from 447 in 2003, as the virus began spreading again in five countries that had been free of polio: Burkina Faso, Central African Republic, Chad, Ivory Coast and Sudan. Three other countries -- Egypt, Niger and Nigeria -- have never stopped transmission of polio.
The disease now threatens countries on the Horn of Africa, Congo and the Arabian Peninsula, said Dr. David Heymann, the official in charge of the WHO's polio eradication program. A year ago, polio transmission was confined to Egypt, Niger and Nigeria.
The health organization, a UN agency, attributes the recent spread to the political and religious opposition in northern Nigeria that halted polio immunizations for a year, until last summer. The interruption led to the spread of the disease to 12 formerly polio-free African countries; these are the five where polio is now spreading and the seven where sustained secondary transmission has not been detected.
Nigeria reported most of Africa's 2004 cases -- 763, or 74 percent. The second-highest total was in Sudan, where the number of cases rose to 112 from zero over the last nine months.
Heymann said that health officials who conducted an emergency polio immunization program there last week reported that the incidence had peaked. The meeting last week was conducted to follow up on the health ministers' declaration a year ago that polio would be eradicated by the end of 2004, a year ahead of the health organization's latest target.
This year the ministers pledged to repeat a 2004 program in which 23 African countries immunized 80 million children under the age of five.
The resurgence of polio in Africa is costing an extra US$150 million for the immunization programs, Heymann said.
The immunization effort has begun to slow the spread of the disease, the ministers said. But Heymann cautioned that the incidence of polio usually fell to its yearly low when the climate was dry.
A clearer picture will emerge in the rainy season, when transmission tends to reach its normal high. The polio virus is present in feces, and exposure occurs often when sewage backs up in the rainy season, he said. The virus is often spread through hand-to-hand and hand-to-mouth contact.
Three strains of polio virus can cause paralysis. The vaccine used in the eradication program is aimed at preventing all three types.
Immunizations in Egypt, one of the endemic polio countries, have eliminated two types of polio virus, but for unknown reasons not the one known as polio type 1.
Egypt and the health organization are changing the strategy to eliminate polio in that country by using a vaccine that protects against type 1 only. The vaccine is being made by Sanofi Pasteur, a French drug company, Heymann said.
By immunizing against just type 1 polio virus, the specialists expect that more children will develop immunity to it and increase chances of stopping transmission.