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Volume 31, Number 9—September 2025

Research Letter

Pediatric Case Report and Overview of Autochthonous Tick-Borne Encephalitis, Belgium

Justine De Langhe, Jo Sourbron, Robbe Van Herreweghe, Marjan van Esbroeck, Koen Vercauteren, Tessa de Block, Jasmine Coppens, Daan Jansen, Dorien Van den Bossche, Veerle Staelens, Sarah De Schryver, and Jos Van AckerComments to Author 
Author affiliation: Author affiliations: Ghent University Hospital, Ghent, Belgium (J. De Langhe); Ghent University Faculty of Medicine and Health Sciences, Ghent (J. De Langhe, R. Van Herreweghe); University Hospital KU Leuven, Leuven, Belgium (J. Sourbron); Ghent University Hospital Center for Medical Genetics, Ghent (J. Sourbron); Institute of Tropical Medicine Antwerp, Antwerp, Belgium (M. van Esbroeck, K. Vercauteren, T. de Block, J. Coppens, D. Jansen, D. Van den Bossche); AZ Sint-Lucas Gent, Ghent (V. Staelens, S. De Schryver, J. Van Acker)

Main Article

Table

Details of autochthonous tick-borne encephalitis cases in a child compared with 3 previous cases in adults, Belgium*

Characteristic Patient no. from 2021 report (6)
 Case report from 2024 (this study)
1 2 3
Age of onset, y/sex
 48/F
 59/M
 58/M
 6/F
Tick bite†
 2 weeks before symptom onset
 2 weeks before symptom onset
 Multiple tick bites in the weeks before symptom onset
 No observed tick bite, but increased outdoor
 activities
Likely site of tick bite, postal code (province)‡
 Oostkamp, 8020 (West Flanders)
 Lille, 2275 (Antwerp)
 Wanze, 4520 (Liège)
 Evergem, 9940 (East Flanders)
Signs/symptoms
During first (viremic) phase Myalgia, fever Fever, fatigue, myalgia, headache Dyspnea, cough, fever Recurrent fever, diarrhea, anorexia, arthralgia (ankles, hands and wrists), myalgia, ophthalmalgia, cervicalgia
During second (neurotrophic) phase Asthenia, tremor, drowsiness, fever, peripheral facial palsy, brachial weakness, nuchal rigidity Fever, fatigue, myalgia, headache, paraparesis, signs of meningitis,
severe motor polyradiculitis		 Recurrent fever, severe and persistent headaches, weakness, diarrhea, anorexia Spiking fever, photophobia, vomiting, agitated behavior, fatigue, myalgia, arthralgia, diarrhea
At follow-up (time)
 Weakness of right arm, loss of cognitive function, inability to concentrate, fatigue, tremor (≈2 mo)
 Improved motor skills 9 mo after hospitalization (wheelchair at discharge)
(9 mo)
 Occasional headaches, otherwise recovered
(≈2 mo)
 No residual symptoms
(6 mo)
Sample type (no. days after symptom onset) Serum (5), CSF (6) Serum (20), CSF (18) Serum (2), serum (18) Serum (5), serum (17), CSF (17), serum (19), serum (26)
Flavivirus IFA serum (no. days after symptom onset) Serum (5): IgM, TBEV+; IgG, TBEV+ Serum (20): IgM, TBEV+; IgG, TBEV+ Serum (2): IgM, TBEV–; IgG, TBEV–. Serum (18): IgM, TBEV+; IgG, TBEV+ Serum (5): IgM, TBEV–; IgG, TBEV–. Serum (17): IgM, TBEV+ (>1/80); IgG, TBEV+ (>1/80). Serum (26): IgM, TBEV+ (>1/80); IgG, TBEV+ (>1/80)
Flavivirus IFA CSF (days after symptom onset) CSF (6): IgM, TBEV+;
IgG, TBEV+		 CSF (18): IgM, TBEV+; IgG, TBEV+ ND CSF (17): IgM, TBEV+; IgG, ND (sample too small for both Ig types)
PRNT90 titer (no. days after symptom onset) Serum (5): 1:25; CSF (6): ND Serum (20): 1:60; CSF (18): ND Serum (2): XXX; serum (18): 1:194 Serum (26): 1:204
rRT-PCR (no. days after symptom onset) Serum (5): ND; CSF (6): ND Serum (20): ND; CSF (18): ND Serum (2): +; serum (18): ND Serum (5): + (Ct 36.27); serum (17): ND; CSF (17): ND; serum (19): ND; serum (26): ND
TBEV RNA sequencing (serum) ND ND ND European subtype TBEV

*Additional case characteristics are provided in Appendix Table 2. CSF, cerebrospinal fluid; Ct, cycle threshold; IFA, indirect fluorescent antibody; ND, not determined; PRNT90, 90% plaque reduction neutralization test; rRT-PCR, real-time reverse transcription PCR; TBEV, tick-borne encephalitis virus; +, present/positive; –, absent/negative. †Early removal of the tick might not prevent encephalitis ​(4)​. Approximately 30% of cases occur without a reported tick bite ​(2,4)​. ‡Locations show no clear proximity (Appendix Figure 3).

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References
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Page updated: August 19, 2025
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