Aspects of West Nile Neuroinvasive Disease in a City of Northern Italy from its First Report in 2008 to the 2018 Outbreak

Background West Nile disease (WND) was first recorded in Italy in 2008, mainly in Northern areas near the Po river. Around 1% of cases present as West Nile neuro-invasive disease (WNND). Since 2008, WND is endemic in Ferrara, a small city of North-East Italy. In 2018 an autocnous outbreak was recorded with an early start of WN virus transmission. Methods We retrospectively and prospectively identified all WNND cases recorded in Ferrara province from 2008 to 2018 and recorded epidemiological and clinical features, diagnostics and outcome. Results: In 2018 we recorded 15 WNND cases, 12 males, 3 females (M: F=4:1), mean age 78.5 years with 80% >74 years. In 2008-2017 period 33 WNND cases were recorded, 27 males, 6 females (M:F= 4.5:1), mean age 66.3 years. Incidence rate was 39.8 cases/1 million people compared to 4.5 cases/1 million people registered in the 2008-2017 period. In 2018, 3/15 cases occurred living in the urban centre, compared to 2008-2017 period (4/33 cases; p > 0.05). Of the 15 cases registered in 2018, 73.3% presented history of hypertension, 60% cardiovascular disease, 20% immunosuppression, 20% dementia, 66.5% presented more than one comorbidities. As in 2008-2017 period (32/33 cases), the most common clinical presentation was encephalitis (13 cases). 100% presented fever, 33.3% transient muscular weakness 26.7% speech impairment (aphasia/dysarthria). 9/15 patients died. No association between comorbidities and outcome (survival/death) was found (p>0.05). Fatality rate was 60% in 2018, while 39.4% in 2008-2017 period (p>0.05). Cerebrospinal fluid (CSF) IgM were positive in 12 cases, whereas WNV-RNA PCR, in 6 cases (p<0.05). Conclusions In Ferrara in 2018 a WNND outbreak was registered, epidemiological and clinical features were not statistically different from those of previous years. The 2018 outbreak fatality rate was higher compared to previous years, but not statistically significant. WNND cases were mainly >74 year-old males, with cardiovascular diseases, presenting with encephalitis. Comorbidities did not associated with outcome (p>0.05). CSF IgM testing was more sensitive than WNV-RNA PCR.