Going, going, almost gone. But never quite. It's a pattern that's repeating itself with an ugly regularity. Just as Mumbai begins to hope that it is finally getting rid of the spectre of polio, a case pops up in some slum. And it is back to square one, with renewed mass immunisation drives, door-to-door rounds and mop up programmes. Recently, as health authorities received the stool test reports of Mohammed Asif, a one-year-old boy from Lotus Colony slum in Govandi in north-east Mumbai, there was an air of resignation. He had tested positive for polio. It was small consolation that he was infected with the P3 strain, which is less virulent and more localised in its spread than the deadlier PI. The bigger blow was the knowledge that Asif had contracted the disease despite being administered the vaccine 10 times since birth