Scientists are celebrating a milestone in the global fight against polio with the news that the second of the three known strains of poliovirus now appears to have been eliminated after mass vaccination campaigns.

Wild poliovirus type 2 was eradicated in 1999 and type 3 hasn’t been seen in over two years. However, the news comes as polio type 1 cases in Pakistan are rising, and new cases are reported in South Sudan and Madagascar.

Poliomyelitis is a highly infectious virus which causes paralysis in one out of 200 cases. It commonly targets young children and can cause death when the muscles which aid breathing stop working.