A World Health Organisation spokesperson has said it is very likely that polio has infected people in the Gaza Strip, in what would be a setback for global efforts to eradicate the disease, Reuters reports.

The WHO’s Christian Lindmeier told a UN press briefing that people had probably already been infected in Gaza but that detecting cases can be difficult since most cases of the potentially deadly viral disease are asymptomatic.

“Having vaccine-derived poliovirus in the sewage very likely means that it’s out there somewhere in people,” he said. “So the risk of [it] … spreading further is there and it would be a setback definitely [for global efforts].”

He said an investigation and risk assessment was underway in Gaza.

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