The World Health Organization welcomed an "historic step" towards a polio-free world on Thursday as an expert panel certified that the second of three types of the crippling virus has been eradicated globally.
The announcement by the Global Commission for the Certification of Poliomyelitis Eradication means that only wild polio virus type 1 is still circulating, after type 2 was declared eradicated in 2015, and type 3 this week.
Global polio cases have been cut by more than 99% since 1988, but type 1 polio virus is still endemic in Pakistan and Afghanistan, where it has infected a total of 88 people this year. That is a resurgence from a record low global annual figure of 22 cases in 2017.
"The eradication of wild polio virus type 3 is a major milestone towards a polio-free world, but we cannot relax," said Matshidiso Moeti, the WHO regional director for Africa.
Seth Berkley, chief executive of the GAVI vaccine alliance, said it was "a tremendous victory in the fight against polio."
Polio invades the nervous system and can cause irreversible paralysis within hours. It cannot be cured, but infection can be prevented by vaccination - and a dramatic reduction in cases worldwide in recent decades has been due to intense national and regional immunization campaigns in babies and children.
In unvaccinated populations, however, polio viruses can re emerge and spread swiftly. Cases of vaccine-derived polio can also occur in places where immunity is low and sanitation is poor, as vaccinated people can excrete the virus, putting the unvaccinated at risk.
The Philippines last month said it was planning an emergency vaccination campaign after polio re-surfaced and caused the first two recorded polio cases there for 20 years.
Moeti urged governments to be vigilant: "Countries must strengthen routine immunization to protect communities, ramp up routine surveillance so that we are able to detect even the slightest risk of polio re-emerging," she said in a statement.