International travel had the biggest impact on death rates for countries which were worst hit during the first wave of the coronavirus pandemic, a study suggests.

Researchers from the University of Aberdeen examined a range of factors including border arrivals, population density, the percentage of people living in urban areas, age, average body mass index and smoking prevalence.

They found an increase of a million international arrivals was associated with a 3.4% rise in the mean daily increase in Covid-19 deaths during the first wave of the pandemic across the 37 worst-hit countries.

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Tiberiu Pana, medical student and author of the study, said: “We found that international travel was the strongest predictor of mortality increase.

“Another factor which appeared to play an important role was country-level BCG vaccination coverage, increases in which may be associated with decreases in death rates.

“Nevertheless, these associations were weaker and further work looking at individual patients is required to clarify these potential relationships.

“Our assessment of available data indicates that very early restrictions on international travel might have made a difference in the spread of the pandemic in western Europe, including the UK.

“These findings are particularly important as the world looks to control future waves and strains of the Covid-19 pandemic and prevent related deaths.”

HeraldScotland:

The work focused on the early stages of the pandemic, using international travel data for 2018 as a proxy for 2020 data before international travel restrictions were imposed.

It comes as the discovery of the South Africa strain of coronavirus has prompted travel restrictions.

Most people arriving from anywhere outside the UK, Ireland, the Channel Islands or the Isle of Man must isolate at home for 10 days and provide a negative Covid-19 test result before they travel.

A system of quarantine is due to be introduced in the coming weeks that will further require those arriving from some countries to isolate in hotels.

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Labour has urged the UK Government to go further and bring in a hotel quarantine system for all international arrivals as a way of keeping out mutant strains.

Professor Calum Semple, a member of Government advisory group Sage, has previously said that while it is important to restrict the movement of people as much as possible, it is not practical to close the UK’s borders completely.