Polio: WHO declares type 3 poliovirus eradicated after 31 year campaign

Type 3 wild poliovirus has become the third human pathogen in history to be eradicated, following smallpox and type 2 wild poliovirus. Only type 1 wild poliovirus remains in circulation, the World Health Organization announced on 24 October.

The news is a morale boost for the global campaign to eradicate polio, which has had a difficult year as vaccine refusals and deadly attacks on polio workers have hampered immunisation efforts. Overall, the disease has made a small comeback since 2017, with case numbers now rising for the first time in decades.

Certifying the disappearance of a polio type is a long and painstaking process overseen by the Global Commission for the Certification of the Eradication of Poliomyelitis. It is seven years since type 3 poliovirus was last identified in the wild, in Nigeria. Over 1.5 million faecal or sewage samples have since been tested around the world, with no type 3 viruses found.

Declaring eradication triggers a global effort to account for and secure all samples held in laboratories. The same process occurred …