The Netherlands is banning flights from the U.K. for at least the rest of the year in an attempt to make sure that a new strain of coronavirus that is sweeping across southern England does not reach its shores.

The ban came into effect Sunday morning and the government said it was reacting to tougher measures imposed in London and surrounding areas on Saturday by British Prime Minister Boris Johnson. The Netherlands said it will assess “with other European Union nations the possibilities to contain the import of the virus from the United Kingdom.”

Johnson said a fast-moving new variant of the virus that is 70% more transmissible than existing strains appears to be driving the rapid spread of new infections in London and southern England.

“There’s no evidence to suggest it is more lethal or causes more severe illness,” the prime minister stressed, or that vaccines will be less effective against it.

The Dutch government is already strongly advising its citizens not to travel unless absolutely necessary.

There was no immediate word on what the Dutch government intended to do about the ferries that travel between the U.K. and the Netherlands.

Britain has alerted the World Health Organization that the new variant identified this week appears to be accelerating the spread of COVID-19, saying it accounted for some 60% of the capital’s cases.

Viruses mutate regularly, and scientists have found thousands different of mutations among samples of the virus causing COVID-19. But many of these changes have no effect on how easily the virus spreads or how severe symptoms are.

Britain has seen over 67,000 deaths in the pandemic, the second-highest confirmed toll in Europe after Italy. The Netherlands has recorded over 10,500 virus-related deaths.

(AP)