In October 2019, the World Health Organization (WHO) announced the eradication of type 3 poliomyelitis. This followed the eradication of type 2, which was announced in 2015. Only type 1 remains in the wild, but the CDC, WHO, and other involved public health institutions are optimistic that it can be eradicated soon.
When will the WHO certify the worldwide eradication of all three serotypes of poliovirus?
Types 2 and 3 have already been certified eradicated, but it's not impossible that the wild types could re-emerge naturally. (This actually happened in Nigeria in 2016, two years after the prior last reported natural cases in Africa.) This property of the virus has caused some reticence by the WHO about certifying the eradication--the last known type 2 case was in 1999, but the WHO didn't certify it until 2015. If another wild strain of type 2 or 3 re-emerges before the WHO certifies the worldwide eradication of type 1, this question will not be resolved until the WHO certifies the eradication of type 1 AND recertifies the eradication of the re-emergent type (or publicly declines to de-certify the earlier eradication).