Polio has been eradicated from most parts of the world as part of a decades-long effort by the World Health Organization and its partners to eradicate it. But polio remains one of the world’s most infectious diseases and is still spreading in some countries. WHO and its partners want to eliminate polio within the next few years.
Until it is eradicated from the planet, the virus will continue to spread wherever children are not fully vaccinated. A recent case of polio infection in an unvaccinated child in Gaza is the first reported case of the disease in the region in more than 25 years.
What is polio?
Polio is an infection caused by a virus that mostly affects children under age 5. Most people infected with polio have no symptoms, but it can cause fever, headache, vomiting and spinal stiffness. In severe cases, polio can invade the nervous system and cause paralysis within hours, according to the WHO. The UN agency estimates that 1 in 200 polio cases result in permanent paralysis, usually in the legs. About 10% of paralyzed children die when their breathing muscles become paralyzed.
The virus spreads from person to person, entering the body through the mouth. It is often spread through contact with an infected person’s feces or, less frequently, through contaminated water or food.
How bad was polio in the past?
Too bad. Polio has existed for centuries; ancient Egyptian hieroglyphics depict children walking with canes, with the characteristic weak limbs of polio victims.
Before the first vaccine was developed in the 1950s, polio was one of the most feared diseases. An explosive outbreak in New York in 1916 killed more than 2,000 people, and the worst outbreak in the US in 1952 killed more than 3,000. Many polio survivors suffered lifelong consequences, including paralysis and deformed limbs. Some people had paralyzed breathing muscles, so they needed “iron lung” chambers to help them breathe.
When did the eradication campaign start?
The WHO passed a resolution to eradicate polio in 1988, inspired by the success in eradicating smallpox eight years earlier. Their original goal was to eliminate polio by 2000. The WHO – along with partners including the U.S. Centers for Disease Control and Prevention, UNICEF and Rotary International – promoted the production of an oral vaccine and launched a massive vaccination campaign. Polio cases were reduced by more than 99%.
Afghanistan and Pakistan are the only countries where polio has never been eradicated. There are also more than a dozen other countries endemic to polio, most of them in Africa. The WHO and its partners now aim to eradicate polio by 2026.
Why did it take so long?
This is extraordinarily difficult. Stopping polio outbreaks means vaccinating at least 95% of the population everywhere, including conflict-torn countries and poor areas with broken health systems and other priorities.
The oral vaccine is cheaper, easier to use and better at protecting entire populations from getting infected. But it contains weakened, live polio virus and in very rare cases it can spread to unvaccinated people and cause polio. In even more rare cases, the live virus from the vaccine can mutate into a new form capable of starting new outbreaks.
Health officials have become more successful in reducing the number of cases caused by wild poliovirus. Vaccine-related cases now cause the majority of infections worldwide.
“The problem with trying to eradicate polio is that the requirement for perfection is very high and there are a lot of weak links,” said Scott Barrett, a Columbia University professor who has studied polio eradication. “The technical feasibility is there, but we live in a very imperfect world.”
