Dr David Nabarro said "it's as though we're just passing the halfway mark on a marathon" and it is still not clear how long it will take to reach the end because of the way coronavirus "challenges and surprises".

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He also criticised politicians and those who continue to make "amazing predictions" claiming COVID should be treated like the flu - while the WHO has said global governments "should not suggest to people" that the "virus has suddenly got incredibly weak".

'Very nasty and rather cunning'

COVID is a "new virus, and we must go on treating it as though it is full of surprises, very nasty and rather cunning," he warned.

When asked by Kay Burley whether the end of COVID could be on the horizon in Europe, Dr Nabarro said: "The end is in sight - but how long is it going to take to get there and what sort of difficulties will we face on the way?

"Those are the questions that none of us can answer because this virus continues to give us challenges and surprises."

He continued: "I do want everybody to do one thing - and that is to go on treating this virus with respect. It has not changed. It's absolutely not suddenly become a soft thing - it is still very serious.

"So for me, if the end is in sight, that's good news. But it's as though we're just passing the halfway mark on a marathon and we can see that, yes, there is an end and the fast runners are getting through ahead of us.

"But we've still got a long, long way to trudge and it's going to be tough."

Plan B restrictions will come to an end in England on Thursday with the relaxing of restrictions surrounding face masks, vaccine passports and working from home.

More variants 'not far away'

When asked about Health Secretary Sajid Javid's comments that COVID should be treated like the flu, Dr Nabarro said: "I keep wondering what the people who make these amazing predictions know that I and my colleagues in the World Health Organisation don't know.

"You see, what people are seeing from around the world and reporting to the WHO is this is still a very, very dangerous virus, especially for people who have not been vaccinated and who've not been exposed to it before.

"It also can mutate and form variants and we've seen several - but we know there are more not far away.

"So quite honestly, we are not saying that this should be considered to be like flu or indeed like anything else.

Dr Nabarro added: "All I'm asking every leader in the world to do is to help everybody stay focused on the job which is keeping this virus at bay, preventing people from getting infected if at all possible and making certain that we are well prepared to deal with further surges as they come."