Tick-Borne Encephalitis in Norway: A Cohort Study of Clinical Course and Health-related Quality of Life at three- and twelve-month follow-up

Abstract Purpose Knowledge of tick-borne encephalitis (TBE) prognosis is limited. This study aimed to describe the disease course in the first year and assess one-year outcomes, focusing on clinical recovery and health-related quality of life (HR-QoL). Methods In this cohort study, we recruited hospitalized patients ≥ 16 years with confirmed TBE from hospitals in Norway's endemic area. A clinical composite score consisting of variables on symptoms and neurological findings was scored at baseline (during hospitalization), 3- and 12 months. HR-QoL at 12 months was measured using RAND 36-item short form health survey and compared to the Norwegian reference population. Results Among the 93 patients included, clinical improvement from baseline to 3 months was 68%, increasing to 77% by 12 months. The proportion of patients with symptoms or neurological findings influencing daily life was 98% at baseline, 52% at 3 months, and 41% at 12 months. 14% required inpatient rehabilitation, and 7% of active workers were on full-time sick leave at 12 months. Severe disease and comorbidities were linked to poorer outcomes. Most common symptoms influencing daily life at 12 months were fatigue (28%), concentration issues (13%) memory and sleep difficulties (12% each), while 8% had clinical findings where impaired balance and tremor dominated. Patients scored lower in physical health and social functioning regarding HR-QoL than reference population. Conclusion Most improvements occur during the 3 three months; however, 42% of patients experience ongoing complaints at 12 months, impacting HR-QoL regarding physical health. Severe disease and comorbidities correlate with poorer prognoses.