Polio just got one step closer to becoming the second human disease to be fully wiped out. During the last World Polio Day, the World Health Organization announced that type 3 poliovirus has been eradicated worldwide.
For polio to be fully eradicated, all three wild polio strains — types 1, 2, and 3 — need to stop circulating. The three strains all cause the same horrible symptoms, including paralysis and death, but are virologically distinct.
Type 2 was eradicated back in 2015; the last case of type 3 polio surfaced in northern Nigeria in 2012 and the virus hasn’t been seen since. A poliovirus can be considered eradicated if it hasn’t been detected for three years.