A new strain of COVID-19 has nations wary of the United Kingdom.

A new strain of COVID-19 has been confirmed to have developed in the United Kingdom. According to medical experts, this new strain does not make illness resulting from the virus any more severe, but it does make it much more contagious. As a result of these reports, at least 40 countries have temporarily banned travel to and from the UK.

This new strain is believed to have first manifested in the UK as early as September, and based on available statistics, currently accounts for at least two-thirds of the total COVID-19 infections in the UK right now. Viral experts estimate the new strain to be about 70% more infectious than the normal coronavirus due to a particular combination of viral mutations.

The reports have prompted a mass exodus from major British cities as citizens try to escape from crowded areas. London in particular saw a massive influx of travelers at local train stations. Those leaving the country, either as part of the aforementioned exodus or for holiday travel, have had their options drastically reduced. However, travel between the UK and the United States is still open, in spite of US calls to close down British flight paths.

At the behest of New York Governor Andrew Cuomo, British Airways and Delta Airlines have begun testing passengers traveling from London to New York in an effort to keep the new strain from spreading to New York and the United States, though some reports claim it has already made its way here.

Epidemiologists are not yet sure if this new strain will react differently to the newly approved Pfizer and Moderna vaccines, though so far there does not seem to be any evidence of lessened vaccine efficiency.

“Right now, there’s no evidence that this new variant will make our vaccine less effective or that it will make tests less effective,” said Dr. Caitlin Rivers, an epidemiologist from John Hopkins University.