Infectious Disease: Evolving Challenges to Human Health

Progress Toward Polio Eradication

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Polio was once a worldwide disease, paralyzing more than 1,000 children per day in 125 countries. By 2003, polio was found in only six countries because of intensive vaccination campaigns. In order to break chains of virus transmission from child-to-child, countries held National Immunization Days (NIDs) with the goal of vaccinating every child under the age of five within a few days. Massive mobilization of vaccine shipments and volunteer health workers were needed to achieve these results. Even war-torn nations negotiated ceasefires in order to hold NIDs.

World Health Assembly passes a resolution to eradicate polio by 2000.
The Americas certified polio-free. In 2000, the lack of wild polio in the United States prompted a switch from the live attenuated oral vaccine, which rarely can cause polio, to the killed virus vaccine, which must be injected but cannot cause polio.
550 million children vaccinated worldwide (~10% of the global population); 17 African countries synchronized NIDs and vaccinated 76 million children; Western Pacific region certified polio-free.

500 million children vaccinated worldwide; 99% of reported cases are in India, Pakistan, and Nigeria; European region certified polio-free.
Polio remains endemic in six countries: Nigeria, India, Pakistan, Niger, Afghanistan, and Egypt.
Polio remains endemic in four countries Nigeria, India, Afghanistan and Pakistan. Cases were imported into Somalia, Namibia, Bangladesh, Ethiopia, Niger, Democratic Republic of the Congo, Indonesia, Yemen, and Nepal.

2003 Lapse Shows Vaccine Effectiveness
In August of 2003, public figures in the state of Kano, Nigeria, expressed concerns that the oral polio vaccine had been deliberately contaminated with an anti-fertility agent. Immunization stopped immediately and new polio cases increased locally from 50 to well over 200 within one year. The epidemic rapidly spread to ten neighboring African nations where it had been eradicated. The World Health Organization launched an emergency vaccination program across Africa to contain the epidemic and immunizations ultimately resumed in Nigeria. The rapid spread of the poliovirus to many nations demonstrates vaccination programs must be thorough and consistent in order to eradicate a disease.

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