The first case of West Nile fever for 2026 has been officially registered in Bulgaria. The information was announced by the National Center of Infectious and Parasitic Diseases in their weekly report for the period of August 17–23, 2026.

Statistics show that last year, during the same interval—from January to August 23, 2025—one case of the disease was also recorded. The infection is vector-borne and is transmitted through the bite of infected mosquitoes of the genus Culex, which carry the virus after feeding on infected birds.

According to data from the Center, the frequency of cases is highest during the period from July to September, when mosquito activity is at its peak. In 80% of cases, infected individuals show no symptoms. In the remaining 20%, West Nile fever develops, accompanied by fever, headache, muscle aches, fatigue, vomiting, rash, swollen lymph nodes, and eye pain.

The incubation period of the virus ranges from 3 to 14 days. Transmission from person to person is possible only through organ transplantation or blood transfusion, as well as from mother to child during pregnancy, childbirth, and breastfeeding. At present, there is no vaccine or specific treatment, and doctors only provide supportive therapy.