About 21 deaths have been recorded so far as a result of West Nile Virus which has claimed six lives in Serbia in the past week alone.
This would be the country’s worst hit by the disease health officials said on Wednesday.
That puts the number of confirmed infections in Serbia at 213, most of them in the capital, Belgrade, according to the national public health institute
Greece is the next worst-affected country, with five dead in the past week for a death toll of 16 and 130 cases registered.
In Greece, the disease has focused on three areas: the Peloponnese Peninsula; around Athens; and around Thessaloniki in the north, the Greek news agency ANA-MPA reported.
In the region, fatalities were also confirmed in Romania and Kosovo and the infection was detected in Croatia and Bosnia.
The virus has probably spread further, but remains undetected as most people overcome the infection with mild symptoms at worst and do not seek a doctor.
The virus is usually spread by mosquitoes and peaks when the insects are the most active, in warm weather, typically in July and August in Europe.
Around 80 per cent of infected people show no symptoms, while the rest display signs similar to the flu: fever, aches, fatigue and swelling of the lymph nodes.
The disease is potentially lethal, usually among older patients, when it leads to encephalitis or meningitis.