On the map
The global retreat of polio on a map, 1980–2023
In 1980 more than 50,000 cases of paralytic polio were reported across 112 countries. By 2016 the map had shrunk to 42 cases in four countries. Polio is the clearest example of a disease map being erased country by country, and a reminder that the last dots are the hardest to remove.
See this on the map ↗1980: polio almost everywhere
In 1980, India reported 18,975 paralytic cases, China 7,442, Sudan 4,151, Pakistan 2,980 and Egypt 2,006. Reports still understated the burden. When the eradication campaign began in 1988, WHO estimated about 350,000 cases a year in more than 125 endemic countries, ten times the 34,617 that were reported.
1988: a plan to erase the map
The World Health Assembly launched the Global Polio Eradication Initiative in 1988. The strategy combined routine infant vaccination, mass campaigns on national immunization days, and surveillance for acute flaccid paralysis, so that every case of sudden weakness in a child is investigated.
The map follows the result. Reported cases fell below 10,000 by 1994 and below 3,000 by 2000. The number of countries reporting cases fell from 87 in 1988 to 31 in 2000.
Region by region
Whole WHO regions were certified free of wild poliovirus one after another. The Americas were certified in 1994, the Western Pacific in 2000 and Europe in 2002. South-East Asia followed in 2014, three years after India’s last case. Africa was certified in August 2020, four years after the last wild case was recorded in Nigeria.
Two of the three wild poliovirus types are gone: type 2 was declared eradicated in 2015 and type 3 in 2019.
2016: the smallest map
In 2016 the map shows only four countries: Pakistan (21 cases), Afghanistan (13), Nigeria (5) and Laos (3). It is the lowest total in the series.
Why polio came back onto the map
The series counts wild poliovirus and circulating vaccine-derived poliovirus (cVDPV). The weakened virus in oral polio vaccine can, in rare cases, circulate for a long time in communities where too few children are immunized, and regain the ability to paralyse. Syria reported 74 such cases in 2017.
Cases rose to 1,253 in 2020, when vaccination campaigns paused during the COVID-19 pandemic. Afghanistan (364) and Pakistan (219) had wild and vaccine-derived cases, and Chad, the Democratic Republic of the Congo, Burkina Faso and Côte d’Ivoire had vaccine-derived outbreaks. In 2023 the largest counts came from the Democratic Republic of the Congo, Nigeria and Chad, almost all vaccine-derived. The answer is higher vaccination coverage, including with newer, more genetically stable oral vaccines.
How to read the polio map
The map counts paralytic cases only. According to WHO, about one in 200 polio infections leads to irreversible paralysis, so each case stands for many infections that were never seen. The annual series ends in 2023.
Common questions
Has polio been eradicated?
Not yet. Wild poliovirus types 2 and 3 are eradicated, but type 1 remains endemic in Pakistan and Afghanistan, and vaccine-derived outbreaks still occur elsewhere.
Where does wild polio still exist?
Only in Pakistan and Afghanistan, according to WHO.
What is vaccine-derived polio?
A rare strain that develops when the weakened virus in oral vaccine circulates for a long time in poorly immunized communities. More vaccination, not less, stops it.
Why does the map show more polio cases in 2020 than in 2016?
The series includes vaccine-derived cases, which rose as immunity gaps widened and campaigns paused during COVID-19.