The measure is due to a new coronavirus strain which has been reported to have spread in the UK

As of today, Bulgaria has introduced a ban on all arrivals from Great Britain and Northern Ireland through all entry points and with all modes of transportation. The ban will be in force from December 21 to January 31, 2021, an order of Bulgaria's Minister of Health issued late last night reads. All flights arriving from the UK have been suspended until January 31.

The ban does not apply to Bulgarian citizens and persons with a status of permanent, long-term or continuous residence in Bulgaria and their family members. Upon entry in Bulgaria, they will be subject to a 10-day quarantine in their homes or in another place of accommodation indicated by them. 

The measure is due to a new coronavirus strain which has been reported to have spread in the UK.
The decision for the new travel restrictions was taken at an emergency meeting last night of PM Boyko Borissov with Foreign Minister Ekaterina Zaharieva, Transport Minister Rosen Zhelyazkov and Health Minister Kostadin Atanasov.

The passengers who arrived in Bulgaria with the last three flights from Great Britain have been quarantined. As an exception, they were allowed to land on December 21. The passengers are mostly Bulgarian citizens returning the Bulgaria.