# Tick-borne encephalitis in Norway: A cohort study of clinical course and health-related quality of life at three- and twelve-month follow-up

## TL;DR

This study tracks the recovery of tick-borne encephalitis patients in Norway over one year, showing most improvement happens early but many still face long-term health issues.

## Contribution

The study provides detailed longitudinal data on TBE recovery and HR-QoL outcomes in a Norwegian cohort.

## Key findings

- 77% of patients showed clinical improvement by 12 months, but 41% still had symptoms affecting daily life.
- Fatigue, concentration issues, and sleep difficulties were the most common long-term symptoms.
- Patients scored lower in physical health and social functioning compared to the general population.

## Abstract

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).

In this cohort study, we recruited hospitalized patients ≥ 16 years with confirmed TBE from hospitals in Norway’s endemic area. A composite clinical 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.

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 4/56 (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.

Most improvements occur during the first three months; however, 41% of patients experience ongoing complaints at 12 months, impacting HR-QoL regarding physical health. Severe disease and comorbidities correlate with poorer prognoses.

Project #2,296,959 – The NOrwegian Tick-borne Encephalitis Study – NOTES. An Observational Study on Clinical Features, Long-term Outcomes and Immune Characteristics – Cristin.

The online version contains supplementary material available at 10.1007/s10096-025-05341-z.