On April 13, The New York Times reported on promising results in global efforts to eradicate polio. Eliminated from endemic spread in the Americas in 1991, polio persists in other areas, particularly in India and Nigeria.
The World Health Organization reports that recorded polio cases are down 75% this year from the same period a year ago. Muslim leaders in Nigeria have begun to support vaccination campaigns, a sharp reversal from earlier claims that vaccination programs had secret aims of sterilizing the population or spreading HIV. And vaccination efforts have focused on remote regions in India, where polio vaccination coverage had been poor.
The Times quoted D.A. Henderson, MD, former director of the World Health Organization’s Smallpox Eradication Programme, on the possibility of polio eradication. Henderson, whom we interviewed a short time ago, seemed encouraged by the new figures, but also called attention to the dangers of polio infection from vaccine virus types. (In 1 in every 2.5 million oral polio vaccine recipients, vaccine-derived poliovirus can mutate to a virulent form. And, in areas with low vaccination coverage, circulating vaccine-derived polio viruses from OPV have led to polio outbreaks and even deaths. See a WHO information sheet for more on this topic.)
Why has polio resisted eradication? Dr. Henderson enlightened us on this topic, while first reminding us of the difficulties of eradicating smallpox: lack of funds and health system infrastructures, political unrest interrupting vaccination campaigns, and vaccine transport and storage difficulties. But polio as a disease presents additional challenges smallpox didn’t. Smallpox had distinctive symptoms, and a person with smallpox was generally not contagious until she showed signs of the disease. Polio, on the other hand, is less visible. Many people infected with polio don’t have any symptoms, while others have mild symptoms that mimic those of other viral diseases. This means that identifying and containing cases of polio present particular challenges to health workers.
See the latest report on wild poliovirus cases from the Global Polio Eradication Initiative.