The new variant of the SARS-CoV-2 coronavirus is spreading rapidly in the UK and prompting high levels of concern around the world. 

COVID-19 cases in Britain are at record levels and the increase in numbers is fuelled by the more transmissible variant of the virus. 

UK Prime Minister Boris Johnson said on Sunday (local time) tougher lockdown restrictions were probably on the way as COVID-19 cases keep rising. 

The UK Government has cancelled the planned reopening of schools in and around London but teaching unions want wider closures.

More than 40 countries have closed their borders to the UK leaving very limited flight options because travellers can't transit through certain countries.

The worsening COVID-19 outbreak in the UK is making it close to impossible for many Kiwis trying to get back home.

On Sunday the Ministry of Health (MoH) announced six cases of the new UK Variant were in New Zealand. 

"The cases are all cared for with the same high level of infection prevention measures as all COVID-19 positive cases, with daily health checks and use of PPE," the MoH said in a statement.

"Infection prevention control protocols are in place for all staff and we can assure the public that there is no increased risk to the community."

COVID-19 Response Minister Chris Hipkins announced on Sunday that from January 15, all travellers from the UK will need to return a negative COVID-19 test prior to departure.

Director-General of Health Dr Ashley Bloomfield said the new cases were expected and were being treated as all COVID cases are treated. 

"There are more than 20 countries that have detected this new variant," Dr Bloomfield said.  

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"The first of those cases was one that arrived in New Zealand on December 13, we do our weekly run of the genome sequencing and they were all picked up in the run that was done on December 30th.

"Remember while this variant is more transmissible, about one and a half times more, the protocols are the same and everyone is treated the same." 

Should we be concerned? 

Most scientists say yes. 

The strain, referred to by some experts as the B.1.1.7 lineage, is not the first new variant of the pandemic virus to emerge, but is said to be up to 70 per cent more transmissible than the previously dominant strain in the UK.

The new variant has rapidly become the dominant strain in cases of COVID-19 in England and has caused an increase in hospitalisation rates.

While it was first seen in the UK in September, by the week of December 9 in London, 62 per cent of COVID-19 cases were due to the new variant. That compared to 28 per cent of cases three weeks earlier.

More than 20 countries have now reported having the strain, including the US and New Zealand.

"It is right to take it seriously," said Peter Openshaw, a professor of experimental medicine at Imperial College London. 

Shaun Fitzgerald, a visiting professor at the University of Cambridge, said the situation in the UK was "extremely concerning".

Why?

The main worry is that the variant is significantly more transmissible than the original strain. It has 23 mutations in its genetic code - a relatively high number of changes - and some of these are affecting its ability to spread.

Scientists say it is about 40 percent - 70 percent more transmissible. 

This means it is spreading faster in the UK, making the pandemic there yet harder to control and increasing the risk it will also spread swiftly in other countries.

"The new B.1.1.7 ... still appears to have all the human lethality that the original had, but with an increased ability to transmit," said Martin Hibberd, professor of emerging infectious disease at the London School of Hygiene & Tropical Medicine.

Will COVID-19 vaccines protect against this variant?

Scientists say there's no evidence that vaccines currently being deployed in the UK - made by Pfizer and BioNtech - or other COVID-19 shots in development will not protect against this variant.

"It's unlikely that this will have anything more than a minor ... effect on the vaccine’s effectiveness," said Adam Finn, a vaccine specialist and professor of paediatrics at Bristol University.

The UK's chief scientific adviser Patrick Vallance also said COVID-19 vaccines appeared to be adequate in generating an immune response to the variant of the coronavirus.

"We are not seeing … any gross changes in the spike protein that will reduce vaccine effectiveness so far," said Julian Tang, professor and clinical virologist at Leicester University.

Does the new variant affect testing?

To some extent, yes.

One of the mutations in the new variant affects one of three genomic targets used by some PCR tests. This means that in those tests, that target area, or "channel", would come up negative.

"This has affected the ability of some tests to detect the virus," said Robert Shorten, an expert in microbiology at the Association for Clinical Biochemistry & Laboratory Medicine.

Since PCR tests generally detect more than one gene target, however, a mutation in the spike protein only partly affects the test, reducing that risk of false-negative results.

Are there other variants about?

Yes. Strains of the COVID-19-causing virus have emerged in recent months in South Africa, Spain, Denmark and other countries that have also raised concern.

However none, so far, has been found to contain mutations that make it more deadly, or more likely to be able to evade vaccines or treatments.