Arthropod-borne
viral infections have recently gained considerable attention and importance as re-emerging
infections in a global scale. West Nile Virus (WNV), a member of Flaviviridae, is an enveloped positive strand RNA virus that is usually transmitted to humans by the
bite of Culicine mosquitoes. Although the majority of the human
infections are asymptomatic, WNV may also cause febrile and neuro-invasive diseases. Seroprevalence data from Turkey indicate that WNV activity is present in Central Anatolia. In this study performed at Hacettepe University Hospital, paired serum and cerebrospinal fluid (CSF) samples from 87 adult patients with the preliminary diagnosis of
aseptic meningitis/
encephalitis of unknown etiology were evaluated retrospectively to identify WNV-related syndromes. Bacterial, fungal and mycobacterial cultures yielded negative results and Mycobacterium tuberculosis and Herpes simplex virus
nucleic acid tests were also negative for the selected patients. Commercial
enzyme-linked
immunosorbent assay (ELISA)s and indirect immunofluorescence test (IIFT)s were employed for WNV
IgM and
IgG antibody detection (Anti-WNV Virus
IgG/
IgM ELISA, Anti-WNV Virus
IgG/
IgM IIFT; Euroimmun, Germany). Additional ELISA/IIFT assays were further performed for WNV antibody reactive samples to identify cross-reactions and/or
infections with other flaviviruses and phleboviruses. All WNV antibody positive samples were also evaluated by a WNV real-time reverse-transcription polymerase chain reaction (RT-PCR) assay. WNV
IgM and
IgG antibodies were detected in %9.2 (8/87) and 3.4% (3/87) of the serum samples, respectively. All
IgG reactive samples were negative for
IgM. All sera with WNV antibody reactivity (n = 11) and the corresponding CSF samples were negative for
viral RNA via RT-PCR. In 5 of the 8 WNV
IgM positive subjects,
sandfly fever virus
IgM antibodies were detected, which was also accompanied by Dengue virus
IgM positivity in one sample. In another case, intrathecal antibody synthesis against measles virus was demonstrated. Two cases (2/87; 2.3%) with WNV
IgM positivity as the only serologic marker were identified as probable
WNV infections and clinical features were discussed. In conclusion, in order to fully understand the impact of WNV and/or other
flavivirus infections in Turkey, epidemiology and ecological features of these agents need to established.