Mosquitoes carrying the West Nile virus were found in areas of northern Israel on Thursday, Israel Radio reported.
The strain was detected in Kiryat Ata, Kiryat Bialik, Kfar Tavor, and Nahal Hilazon in the Galilee.
The Environmental Protection Ministry has advised local authorities on how to deal with the discovery.
Cases of West Nile disease have declined dramatically in recent years. In mid-August, three Israelis were infected with the fever, bringing the annual tally to 15, according to the Health Ministry. By this time last year, some 53 cases were reported, it said.
The cases were reported in various parts of the country, from Ashkelon to Haifa.
According to the ministry, the peak season for the West Nile fever is between August and October, and “the disease is transmitted primarily via Culex pipiens and Culex perexiguus mosquitoes.”
Symptoms include fever, rash, headache, and rarely, more serious side effects such as meningitis could develop.