International travel had the biggest impact on Covid death rates for countries hit in the pandemic's first wave, a study has found.
Researchers in Aberdeen focused on the world's worst affected 37 countries.
They examined factors including border arrivals, population density, the percentage of people living in urban areas, age, and health issues.
The team said early restrictions on international travel could have made a difference in the spread.
The study looked at counties including America, the UK, Spain, France, Italy and Brazil, and focused on the early stages of the pandemic.
They found an increase of one million international arrivals was associated with a 3.4% rise in the mean daily increase in Covid-19 deaths.
The researchers used international travel data for 2018 as a proxy for 2020 before international travel restrictions were imposed, to match travel trends with the pattern of the virus.
Tiberiu Pana, one of the authors of the study, said: "We found that international travel was the strongest predictor of mortality increase.
"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."
The medical student said the level of a country's BCG vaccination coverage also appears to have a played an important role.
Lead author, Prof Phyo Myint, director of the Aberdeen Clinical Academic Training Scheme said: "This is important research, led by medical students, who have demonstrated robust use of publicly available data to inform future policies in preventing the spread of Covid-19."
The study comes as the discovery of the South Africa strain of coronavirus prompted the extension of tougher restrictions for all travellers arriving directly into Scotland,
On Wednesday First Minister Nicola Sturgeon said UK government plans to put people arriving from high risk countries on a "red list" and require them to quarantine in hotels "does not go far enough".
The Scottish government now plans to introduce a "much more comprehensive" approach to "managed quarantine".
Do you have a question about the Covid restrictions in place in Scotland? Use the form below to send us your questions and we could be in touch.
In some cases your question will be published, displaying your name, age and location as you provide it, unless you state otherwise. Your contact details will never be published. Please ensure you have read the terms and conditions.
If you are reading this page on the BBC News app, you will need to visit the mobile version of the BBC website to submit your question on this topic.