Experts have warned that climate change could lead to a spread of tropical mosquito and tick-borne viruses across Europe's borders.
Diseases such as yellow fever, dengue fever, West Nile fever and Japanese encephalitis mostly occur in the tropics and other warm regions of the world.
However, due to the greater movement of people, goods and animals they are becoming more widespread.
A report in The Lancet medical journal said it is likely that global warming would accelerate the spread of these viruses into southern and even northern Europe.
The diseases belong to a family of "flaviviruses" that are transmitted by blood-sucking insects, and one of them, the yellow fever virus, causes up to 200,000 infections and 30,000 deaths in sub-Saharan Africa each year.
At the moment there is no vaccine available against dengue virus, which can produce dangerous fevers and cause the body to go into shock. Both of these viruses are carried by the mosquito Aedes aegypti.
Authors Dr Ernest Gould, from the Centre for Ecology and Hydrology in Oxford, and Professor Tom Solomon, from the University of Liverpool, wrote: "As Aedes aegypti disperses more widely we might... witness dengue virus emerging in warmer regions of Europe and North America."