Poliovirus type 2 returns
The global battle to eradicate poliomyelitis is already 9 years behind schedule. To make matters worse, type 2 poliovirus, which was declared eradicated in 1999, has returned. There are three serotypes of poliovirus, each of which causes poliomyelitis. The vaccine used by WHO in the global eradication effort is a trivalent preparation comprising all three …