Governments in Europe “missed building up the necessary infrastructure during the summer months, after they brought the first wave under control," David Nabarro, a WHO special Covid-19 envoy, said during an interview with Swiss newspapers.
"Now we have the second wave. If they don't build the necessary infrastructure, we'll have a third wave early next year," Mr Nabarro added.
While Europe briefly enjoyed a lull in infection rates, a second wave of the virus is now surging across the continent.
Mr Nabarro criticised Switzerland for allowing skiing, with masks required in gondolas, while other Alpine nations such as Austria have shut down resorts.
He said the country could see a “very high level of sickness and deaths”.
"Once the infection rates sink, and they will sink, then we can be as free as we want," the British expert was quoted as saying by the Solothurner Zeitung. "But right now? Should ski resorts open? Under what conditions?"
Mr Nabarro celebrated the response of Asian countries such as South Korea, which have managed to keep infections at a relatively low level: "People are fully engaged, they take on behaviours that make it difficult for the virus.
"They keep their distance, wear masks, isolate when they're sick, wash hands and surfaces.
"They protect the most endangered groups."
He said Asia did not relax restrictions prematurely, adding: “You must wait until case numbers are low and stay low. Europe’s reaction was incomplete.”
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