A 72-year-old patient sought medical attention for high fever, headache, and gait instability. In July 2018, a 72-year-old female, was admitted to a local hospital due to a three-day fever, progressive frontal and occipital headache, and gait instability. At admission, the patient had a fever of 39.0 °C, while other vital signs were normal. She appeared weary, slow in verbal and motoric responses, but completely oriented. Meningeal signs were negative. Neurological examination revealed symmetric fine intention hand tremor and instability while sitting and walking. Physical examination was otherwise unremarkable, besides irregular pulse due to atrial fibrillation. The patient's laboratory data at admission are presented in Table. Her non-contrast brain multi-slice computed tomography was normal. The spinal tap was postponed for 48 h due to anticoagulation therapy (dabigatran). Empirical therapy with acyclovir 1 g q8 h intravenously and doxycycline 100 mg q12 h orally were administered. On the 6th day, the patient developed somnolence, aphasia, disorientation, urinary retention with asymmetric lower extremity weakness (weaker right leg). Repeated brain multi-slice computed tomography was unremarkable. Spinal tap results are presented in Table. The diagnosis of encephalitis was established. Due to neurologic deterioration, the patient was transferred to the Department for Intensive Care Medicine and Neuroinfectology in a tertiary institution. Past medical history disclosed arterial hypertension, type 2 diabetes, hyperlipidemia, and permanent atrial fibrillation. The patient was taking amlodipine, bisoprolol, metformin, simvastatin and dabigatran. The patient was transferred to a tertiary institution in severely impaired general condition. Her vital signs were as follows: Temperature 36 °C, heart rate 160 beats per minute, respiratory rate 16 breaths per minute, blood pressure 140/85 mmHg and oxygen saturation in room air 95%. She was unable to walk or sit, she was somnolent, opening eyes on demand and demonstrating signs of Wernicke’s aphasia (impaired comprehension with meaningless speech), without obvious signs of cranial nerves’ dysfunction. Muscle tone, strength and deep tendon reflexes were normal on upper extremities, while low on inferior extremities, more on the right side. Plantar response was “silent” on both sides. Abdominal cutaneous reflexes were normal. The patient had urinary catheter placed due to urinary retention. Rectal tone was decreased, the patient was incontinent for feces, and anal wink test was absent. No tremor was noticed. Sensory exam could not be performed due to the patient’s limited communication abilities. The remaining physical examination was unremarkable, besides absolute arrhythmia due to atrial fibrillation. The patient's laboratory results at admission to the tertiary institution are listed in Table. The cerebrospinal fluid (CSF) Gram-stain was unremarkable, the 16S rDNA test of CSF was negative, and the culture did not yield any pathogen. The CSF was further analyzed by polymerase chain reaction and proven negative for herpes simplex virus 1/2, varicella-zoster virus, enteroviruses and Listeria monocytogenes. Anti-HIV, HIV antigen and Treponema pallidum hemagglutination assay were negative. Serology for Borrelia burgdorferi in serum and CSF was negative. CSF, serum and urine samples were tested for the presence of neuroinvasive arboviruses: Tick-borne encephalitis (TBEV), WNV, Usutu (USUV), Toscana (TOSV), Tahyna ˙(TAHV) and Bhanja virus (BHAV). CSF, urine and serum samples were tested using a reverse-transcriptase polymerase chain reaction (RT-PCR): TBEV (Schwaiger et al[]), WNV (Tang et al[]), USUV (Nikolay et al[]), TOSV (Weidmann et al[], 2008), TAHV (Li et al[], 2015) and BHAV (Matsuno et al[], 2013). In addition, CSF and serum samples were tested for the presence of TBEV, WNV and USUV IgM and IgG antibodies using commercial enzyme-linked immunosorbent assays (TBEV, WNV, USUV - Euroimmun, Lübeck, Germany) and indirect immunofluorescence assay (TOSV - Euroimmun, Lübeck, Germany). According to the European Union case definition[], WNV infection was confirmed by detection of IgM and IgG antibodies in both serum and CSF samples. Detection of low IgG avidity index as well as dynamics of IgG antibodies in consecutive serum samples (days 8, 15 and 22) further supported acute WNV infection. WNV RNA was not detected in CSF, urine nor serum samples. Magnetic resonance (MR) imaging of the brain and lumbosacral spine was performed using a 1.5T MR scanner (Symphony; Siemens Medical Solutions, Erlangen, Germany). The brain MR protocol consisted of sagittal T1-weighted spin-echo, axial T2-weighted fast-spin echo, axial T2-weighted fast-spin echo fat saturated, axial fluid-attenuated inversion recovery, pre- and post-contrast axial T1-weighted spin-echo fat saturated. Brain MR demonstrated nonspecific microvascular lesions in the periventricular regions and deep white matter. The lumbosacral MR protocol consisted of sagittal and axial T1 and T2 weighted image; postcontrast sagittal fat saturated T1 weighted image. It demonstrated intensive cauda equina enhancement as shown in Figure ( and ). The electroencephalogram was diffusely irregular and diffusely slow. The electromyoneurography was not performed due to technical issues at the time. The patient was retired, living alone and taking care of herself. Exposure history revealed that the patient lived in a rural suburb in the Karlovac County, about 200 m from the Kupa River. She denied contact with animals. A few weeks before the illness, she noticed frequent mosquito bites and no tick bites. She denied traveling during the past months, as well as vaccination.