Pediatric Chikungunya Fever: Correlation Between Viral Load and Joint Involvement by Ultrasonography

Background: Chikungunya fever (CHIK) is a mosquito-borne viral infection caused by the Chikungunya virus (CHIKV), which has recently re-emerged in tropical regions. Pediatric manifestations may differ from those in adults, but systematic studies in China are scarce. Methods: This retrospective study analyzed 42 laboratory-confirmed pediatric CHIK cases admitted to Foshan First People’s Hospital (Guangdong, China) between July and August 2025. Clinical features, laboratory parameters, and joint ultrasonography findings were collected. Correlations between cycle-threshold (CT) values and joint involvement were evaluated using Spearman and Pearson analyses. Results: Among 42 children (mean age 10.2 ± 4.1 years; 54.8% boys), fever (95.2%), rash (100%), and joint pain (66.7%) were the main symptoms. Abnormal joint ultrasound findings were observed in 83.3% of children with arthralgia but none without it (P < 0.001). Viral CT values were negatively correlated with the number of affected joints (r = –0.47, P = 0.002). Conclusions: This is the first pediatric study from mainland China to systematically integrate viral CT data with joint ultrasonography. Lower CT values (higher viral load) were associated with polyarticular involvement. Combining molecular and imaging indicators may aid early clinical risk identification and regional public-health surveillance of pediatric CHIK.