A type of poliovirus derived from vaccines has been detected in London sewage samples, the World Health Organization and British health officials said on Wednesday, adding that more analysis was underway. No human cases of polio have been found in Britain, where the crippling disease was fully eradicated two decades ago. The WHO said in a statement that “type 2 vaccine-derived poliovirus (VDPV2)” had been found in environmental samples in the British capital. “It is important to note that the virus has been isolated from environmental samples only,” it said, stressing that “no associated cases…