West Nile Virus Lineage 2 Neuroinvasive Infection Presenting as Intraparenchimal Cerebral Hemorrage

Objective: The aim of this retrospective study was to evaluate clinical and laboratory characteristics in adult patients with neuroinvasive West Nile virus (WNV) infections. We also studied the phylogeny and molecular characteristics of some of the WNV strains. Methods: A retrospective analysis was conducted at “Annunziata” Hub Hospital, a secondary referral facility in Calabria region in Southern Italy. Patients with confirmed WNV infection were included in the study. Biochemical and serological analysis of blood and cerebrospinal fluid (CSF), as well as radiological imaging were done. Sample pre-processing, sequencing and bioinformatic analyses were carried out at IRCCS Sacro Cuore Don Calabria Hospital in Negrar di Valpolicella, Verona, Veneto region in North-East Italy. All the analyses were performed on the same whole blood samples used for the laboratory diagnosis. Results: 9 cases of West Nile encephalitis (WNE) were analyzed, involving 8 males and 1 female, with a mean age of 70.33 years (Range, 60 – 85). Encephalitis was confirmed by the demonstration of specific IgM and IgG antibodies in serum using routine serological screening tests. All the patients had specific IgM antibodies at admission and IgG antibodies were present in 90%. The overall average hospital stay was 20.6 days (range, 6 – 46). Six patients made a full recovery with no neurological sequelae after a meanof 35.3days of acute care.30-day mortality rate was 23%. A 63-year-old man developed a fulminat Guillain-Barré syndrome (GBS) and he died after approximately two months because of severe respiratory complications. Two male patients died after 21 and 13 days, respectively, due to intraparenchimal cerebral hemorrage (ICH) as clinical presentation of WNV encephalitis. A third male patient presented with encephalitis and cauda equina syndrome, complicated by diffuse ICH and a concomitant extensive epidural hematoma. This patient was transferred to a rehabilitation long-term care facility and is still alive after a three-month ‘ follow-up, although he is no longer able to walk. Finally, a 66-year-old male patient presented a severe right Bell’s palsy regressing very gradually in about two months. Phylogenetic analysis shows that our sequences are closely related to other southern-Italian and cluster with Central-Southern-Eastern European sequences, while being evidently separated from northern-Italian and Central-Western European ones, belonging to the sub-lineage 2a of the WNV-2, clustering with sequences from the Central-South-Eastern clade, mainly to Hungary. Conclusions: Cerebrovascular complications of WNE may be an important clinical manifestation of WNV neuroinvasive infection. Preliminary data do not allow us to determine whether our strains, closely related to other southern-Italian and cluster with Central-Southern-Eastern European sequences, really presented an increased neurovirulence.