The UK Foreign Office says there were more than 300 cases of West Nile Virus in Greece in 2018 and anyone flying to the country has been told to use mosquito repellent while they're outside.
It has been reported nationally the virus resulted in the death of 50 Greeks leading to the Foreign Office updating their travel advice for the area.
Symptoms of the condition include a fever, headache, tiredness, body aches, nausea, and skin rash.
While it is thought the infection will be rare in UK travellers, a very small number could develop symptoms and if your immune system is weakened by disease, treatment or medication, or if you are aged over 50 years of age and/or have a pre-existing medical condition, you may be at increased risk of developing severe West Nile fever.
The National Travel Health Network adds the condition is not preventable by vaccination so the only thing you can do if you are visiting a country or region where West Nile Virus is known you should take insect bite precautions.
A UK Foreign Office spokesman added: "You should consider preventative measures to minimise exposure to mosquitoes, for example using mosquito repellent when outdoors and closing doors or windows or using screens.
"Visit the National Travel Health Network and Centre website for more information about the transmission season and advice for travellers."
The virus has spread through Greece through migratory birds with other recommendations including wearing long sleeves, avoiding places with stagnant water and using mosquito nets.
Cases have also been reported in Italy (123 with three deaths), Hungary (23), Kosovo (two with one death), Romania (23 with one death) and Serbia (102 cases including nine deaths), according to the National Travel Health Network.