At least three people have succumbed to mosquito-borne West Nile virus in Serbia, according to a report.
The virus was first detected in the US in 1999, according to US government agency Centers for Disease Control and Prevention (CDC).
The virus has been reported in 1,993 cases, resulting in 87 deaths, till the beginning of September, the CDC said.
At least 30 people infected with the virus have been hospitalized, said Olga Djulovic, director of the Belgrade Infective Clinic.
Doctors said the virus was transported to Europe by migrant birds, but few cases have been reported elsewhere in Europe so far.
However, infections have been discovered on animals and birds in Croatia and Serbia, reports said.
Serbian media has criticized health authorities of hiding the truth, instead of taking precautionary measures immediately. But Djulovic said the exact cause of the three deaths was determined only a few days ago.