The Government's threshold for considering quarantine measures is when a country records a seven-day rate of more than 20 cases per 100,000 people.
But a number of local authority areas in West Yorkshire have much higher rates than that.
The latest figures on Friday showed that Bradford, which is already subject to restrictive measures on households being able to meet, had a rate of 45.9 new cases per 100,000 people.
Calderdale and Kirklees, which are also subject to local lockdowns, have a rate of 33.1 and 32.7.
Meanwhile, according to the Croatian Government the rate of confirmed cases in Dubrovnik was 16.5 per 100,000 - well below the country's overall rate as indicated by the UK's Department for Transport this week of 27.4 per 100,000.
The country's rate had risen to 31.4 by Friday.
In the seven days to August 17, the rate of confirmed cases in Zagreb was 37.9 per 100,000.
Croatia's ambassador to the UK said he regretted that the Government here had not taken a regional approach, instead of enforcing a quarantine for people returning from any part of the country.
Igor Pokaz told BBC Radio 4's Today programme: "In Croatia we have, as I said, witnessed these spikes in certain areas - for example in Zagreb in the capital and maybe among the young population.
"But in Dubrovnik, its surroundings and the islands there were very, very few cases. And I deliberately mention Dubrovnik and the islands as that is where most of the British tourists go. "
Austria's latest rate was 21.2 new cases per 100,000 people, up from 11.8 in the previous seven days.
Trinidad & Tobago, which was named alongside Austria and Croatia regarding quarantine measures on Thursday, had a rate of 26.0 per 100,000, up from 13.9.
The rates in Spain and France, which are subject to quarantine for returning travellers, are 86.4 and 30.5 respectively.
Spain's rate has risen from 58.5, indicating UK sunseekers might face quarantine if travelling there for another while.
Portugal, which was moved on to the UK's safe list on Thursday, has a latest rate of 14.1, down slightly from 14.5.
The UK's latest rate for the seven days to August 20 was 11 cases per 100,000 people.
What are the current lockdown restrictions in West Yorkshire?
Health Secretary Matt Hancock announced on Friday that the local restrictions in parts of West Yorkshire will continue.
Parts of Bradford, Calderdale and Kirklees were put into lockdown due to a spike in coronavirus cases.
The measures were announced at 9.15pm on Thursday, July 30 and implemented from midnight the following day.
It means people in these areas will not be able to mix with other households in private homes or gardens.
This means you cannot go to the house of someone else you do not live with.
You also cannot go in their garden.
People in the affected areas can still go to pubs and to restaurants.
However, two households will not be allowed to go together.
The guidance states that people should not "socialise with people you do not live with in other indoor public venues".
It specifies that "indoor public venues" are pubs, restaurants, cafes, shops, places of worship, community centres, leisure and entertainment venues, or visitor attractions.
The guidance warns people to avoid interaction with others.
This is everything you need to know about the current restrictions.