In DepthEpidemiology

In Pakistan, surveillance for polio reveals a paradox

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Science  12 Jan 2018:
Vol. 359, Issue 6372, pp. 142-143
DOI: 10.1126/science.359.6372.142

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Last year polio fighters could smell victory in Pakistan, which many believe will be the last country on Earth to harbor the virus. Cases dropped to an all-time low. Blood tests showed that immunity to the poliovirus had never been higher. Surely, there were not enough susceptible children to sustain transmission, and the virus would burn itself out within a year. Unsettling new findings, however, show it is far from gone. In the most extensive effort in any country to scour the environment for traces of the virus, polio workers are finding it widely across Pakistan, in places they thought it had disappeared. They are wondering "just what the hell is going on" and how worried they should be, says epidemiologist Chris Maher of the World Health Organization in Geneva, Switzerland, who runs polio operations in the eastern Mediterranean region. Does this mean the virus is more entrenched than anyone realized and is poised to resurge? Or is this how a virus behaves in its final days—persisting in the environment but not causing disease until it fades out?