At this time of year wildfires and strikes are usually uppermost in the minds of tourists visiting Greece. But as the country braces for a bumper season, authorities are also warning: beware of being bitten by mosquitoes.

A week after the Foreign Office took the step of including the insects among the potential perils of travel to Greece, health officials are urging holidaymakers to take precautions against West Nile virus following an unprecedented outbreak of the mosquito-borne disease last year.

“There have been enough cases to know that this is now a public health issue,” said Danai Pervanidou who heads the office for vector-borne diseases at the national organisation for public health (Keelpno). “The virus has established itself in Greece through migratory birds and we are recommending that everyone takes personal protective measures such as wearing long sleeves, avoiding places with stagnant water and using mosquito nets and repellent.”

A record 316 people were infected with the virus last year, resulting in the death of 50 Greeks. In a transmission season that began unusually early, laboratory diagnosed cases were reported in both rural and urban areas, according to Keelpno.

Normally those infected with the virus will exhibit no symptoms. While about 20% experience mild, flu-like ailments including fever, headaches and general aches, only 1% will go on to develop a serious illness, according to the US Centers for Disease Control and Prevention.

But among those diagnosed in Greece last year, 243 displayed symptoms of neuro-invasive disease such as encephalitis, meningitis and acute paralysis.

Not since 2012 when there were 262 cases and 35 fatalities has an outbreak been so severe.

Amid rising official concern, the US embassy in Athens has issued a health alert urging citizens to take preventive measures, from cleaning up mosquito breeding areas to keeping grass and shrubs trimmed.

With the country poised this year to receive 31 million visitors – almost three times its population – steps are being rigorously enforced to control infection outbreaks.

Awareness-raising programmes for medical professionals have been stepped up with information leaflets distributed to airports as well as municipal and regional authorities nationwide.

“It is impossible to predict the area of virus circulation because of its complex epidemiology but what we do know is that it has moved from villages and wetlands in rural areas to big urban centres, including the Attica region [around Athens] and Thessaloniki,” Pervanidou told the Guardian. “Just as in winter when we expect an outbreak of influenza, in summer we now have to expect cases of West Nile fever. We have to be prepared.”

Wild bird species serve as reservoirs for the virus with mosquitoes transmitting it after feeding on their infected blood. Horses are as susceptible as humans to infection.

Greece is not alone in reporting a rise in cases of West Nile virus. Italy, Cyprus, Romania and Serbia have also seen an increase. Infection rates in 2018 alone exceeded the total number reported over the past seven years.

“The last case of [2018’s] transmission season in the EU was reported by France at the end of November … an unusually late date of onset,” wrote the European Centre for Disease Prevention and Control, suggesting the period of exposure to the West Nile virus was also getting longer.