The World Health Organization has cautioned against major alarm over a new, highly infectious variant of the coronavirus that has emerged in Britain, saying this was a normal part of a pandemic's evolution.

WHO officials even put a positive light on the discovery of the new strains that prompted a slew of alarmed countries to impose travel restrictions on Britain and South Africa, saying new tools to track the virus were working.

"We have to find a balance. It's very important to have transparency, it's very important to tell the public the way it is, but it's also important to get across that this is a normal part of virus evolution," WHO emergencies chief Mike Ryan told an online briefing.

"Being able to track a virus this closely, this carefully, this scientifically in real time is a real positive development for global public health, and the countries doing this type of surveillance should be commended."

Citing data from Britain, WHO officials said they had no evidence that the variant made people sicker or was more deadly than existing strains of Covid-19, although it did seem to spread more easily.

Countries imposing travel curbs were acting out of an abundance of caution while they assess risks, Mr Ryan said, adding:"That is prudent. But it is also important that everyone recognises that this happens, these variants occur."

WHO officials said coronavirus mutations had so far been much slower than with influenza and that even the new UK variant remained much less transmissible than other diseases, such as mumps.

They said vaccines developed to combat Covid-19 should handle the new variants as well, although checks were under way to ensure this was the case.

The WHO said it expects to get more detail within days or weeks on the potential impact of the highly transmissible new coronavirus strain.

New strain might more easily infect children - UK scientists

Meanwhile, scientists in the UK have said the mutated coronavirus strain could more easily infect children.

Experts say that data indicates it may be able to better spread among youngsters than other strains, but that analysis is still ongoing.

Professor Neil Ferguson, a scientist on the UK government's New and Emerging Respiratory Virus Threats advisory group (NervTag), said that during the second lockdown in England there was an age shift in the distribution of the virus.

Speaking at a Science Media Centre press briefing, Prof Ferguson, of Imperial College London, said: "There is a hint that it has a higher propensity to infect children that may perhaps explain some of the differences, but we haven't established any sort of causality on that but we can see that in the data."

He added: "What we've seen is, during the lockdown in England we saw a general distribution of the virus towards children, and that was true in the variant and the non-variant, and it is what we would expect, given that we had locked down which reduced adult contact but schools were still open.

"But what we've seen over the course of a five or six-week period is consistently the proportion of pillar two cases for the variant in under-15s was statistically significantly higher than the non-variant virus.

"We are still investigating the significance of that."

Prof Ferguson continued: "This is a hypothesis at the moment - it's not been proven.

"But if it were true, then this might explain a significant proportion, maybe even the majority, of the transmission increase seen.

"But a lot more work needs to be done to actually explore this in more detail."

But NervTag member Professor Wendy Barclay, head of the department of infectious disease, Imperial College London, urged caution about what is said regarding spread among children.

She said: "We are not saying that this is a virus which specifically attacks children.

"We know that SARS-CoV-2, as it emerged as a virus, was not as efficient in infecting children as it was adults, and there are many hypotheses about that.

"And again, if the (new) virus is having an easier time of finding an entrance cell then that would put children on a more level playing field."

She added: "Therefore children are equally susceptible perhaps to this virus as adults, and therefore given their mixing patterns, you would expect to see more children being infected.

"It's not just the viruses specifically targeting them, but it's just that it's now less inhibited, if you like, to get into the children."

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Elsewhere, France appears set to end a ban on hauliers crossing the English Channel which was imposed due to fears about the spread of the new coronavirus strain.

French transport minister Jean-Baptiste Djebbari said a protocol would be adopted at a European Union-wide level "to ensure that movement from the UK can resume".

The UK has been cut off from large parts of Europe - and some other areas of the world - as authorities imposed bans on passengers because of concern about the more infectious mutant coronavirus.

The most dramatic intervention came from France, which put in place a ban on hauliers crossing the English Channel with their cargo.

The move has had implications for Irish hauliers who use the UK landbridge to travel to the continent, with Minister for Foreign Affairs Simon Coveney saying around 250 hauliers were affected.

Mr Djebbari said: "In the next few hours, at European level, we're going to establish a solid health protocol to ensure that movement from the UK can resume.

"Our priority: to protect our nationals and our fellow citizens."

The European Union today scrambled to hammer out a coordinated response to a mutated strain of the coronavirus sweeping Britain, after countries cut transport links.

Experts from the bloc's 27 member states held a three-hour crisis meeting in Brussels to come up with options on how to standardise the measures put in place to try to curb the spread of the new variant.

"Participants stated their support for rapid action towards a coordinated EU approach in relation to measures applied to connections with the UK and called for guidelines from the Commission," a European diplomat said.

A string of nations around the continent yesterday began suspending travel from Britain - but the bans have varied in length from just an initial 24 hours in Belgium to 10 days for Germany, and different rules apply to freight.

A source said EU ambassadors will convene tomorrow to try to nail down a unified approach and work out how they can eventually lift the border restrictions with Britain - including by imposing a requirement for tests on all arrivals.

"The important thing is to approve a similar and synchronised regime to have very strict measures, in particular preliminary PCR tests, when the EU decides to lift the measures taken," a European diplomat told AFP.

"We will see if this will be successful on Tuesday."

A German government source told AFP that restrictions on air travel from Britain could be adopted by the entire 27-member EU and that countries were also discussing a joint response over sea, road and rail links.

Hundreds of trucks have been queuing for miles to enter both Dover and Calais ahead of the Brexit deadline at the end of the month.

A Polish government spokesman said flights from Britain to Poland will be suspended starting from midnight tonight due to concerns over a new strain of coronavirus.

British Prime Minister Boris Johnson announced on Saturday that the new strain had led to spiralling infection numbers.

His government tightened its Covid-19 restrictions for London and nearby areas, and also reversed plans to ease restrictions over the Christmas period.

Reporting by Tony Connelly, PA and Reuters