Fatal Case of West Nile Neuroinvasive Disease in Bulgaria

To the Editor: West Nile virus (WNV) is a mosquitoborne flavivirus. Approximately 80% of human infections are asymptomatic, 10%–20% are characterized by an acute febrile illness, and <1% by involvement of the central nervous system (West Nile neuroinvasive disease). Sporadic human cases and small outbreaks of West Nile fever were reported in Europe until the mid-1990s, when the first large outbreak occurred in Romania in 1996. Since then, and especially in recent years, sporadic human cases and outbreaks have been reported in other countries in Europe and neighboring countries on the Balkan Peninsula. A large outbreak of WNV lineage 2 infection occurred in Greece in 2010. Outbreaks have also been reported in other countries in Europe, which showed spread of WNV lineage 2. Some probable cases of West Nile fever were reported to the Bulgarian Ministry of Health on the basic of serologic test results. We report a case of fatal West Nile neuroinvasive disease in a man in Bulgaria. This case was confirmed by detection of specific antibodies against WNV and sequencing of the full virus genome.