Officials in southern and eastern Africa are working to vaccinate 9 million children against polio after a confirmed outbreak in Malawi.
The emergency campaign began in that country this week.
Vaccines are being given by mouth to children everywhere in the country.
The United Nations children's agency, UNICEF, says the larger goal is to expand the vaccination campaign into neighboring Mozambique, Tanzania and Zambia.
UNICEF is working with the governments of those countries and other partners in the area.
Agency officials said there will be three more rounds of vaccinations in the coming months.
The goal is to vaccinate more than 20 million children.
Mohamed Fall is UNICEF Regional Director for Eastern and Southern Africa.
He said: "This is the first case of wild polio detected in Africa for more than five years and UNICEF is working closely with governments and partners to do everything possible to stop the virus in its tracks."
UNICEF, the World Health Organization, the Global Polio Eradication Initiative and other partners are supporting the vaccination campaign.
It began after doctors confirmed in February that wild poliovirus had infected and paralyzed a three-year-old in Malawi's capital, Lilongwe.
Fall warned, "Polio spreads fast and can kill or cause permanent paralysis."
People most commonly contract polio when they drink dirty water.
The virus can be carried in human waste.
Children under the age of five and those living in areas with poor sanitation are most at risk.
Fall considers the shared effort by neighboring countries as critical, noting, "There is no cure for polio, but the vaccine protects children for life."
"We are working," he added, "to make sure parents, as well as community and religious leaders, know how important it is that every child receives their vaccine."
UNICEF has more than 36 million treatments of the polio vaccine for the first two rounds of immunizations in Malawi, Mozambique, Tanzania and Zambia.
In Malawi, UNICEF is providing 270 new vaccine refrigerators and is repairing others.
The agency is also supplying temperature measurement devices, vaccine carriers and cold storage containers.
In partnership with the World Health Organization, UNICEF has trained 13,500 health workers and volunteers, 34 area health officers and 50 religious leaders.
In Mozambique, the children's agency is helping supply vaccines to local stores.
It also assists in training programs about vaccine use for thousands of supervisors, health workers and media providers.
UNICEF is deploying similar efforts in Tanzania and Zambia.
I'm Mario Ritter, Jr.