Influenza-Like Illness in Children With Cancer: Incidence, Predictors, and Outcomes From a Tertiary Cancer Center in India

Background: Influenza-like illness (ILI) is a clinical syndrome caused by multiple respiratory pathogens and does not necessarily represent laboratory-confirmed influenza. Children receiving cancer therapy may experience substantial morbidity and treatment interruption from ILI, but data from low- and middle-income countries remain limited. Objective: To estimate the incidence of ILI, describe its clinical characteristics, management, treatment impact, and outcomes, and identify independent predictors of inpatient management and inpatient duration in children receiving cancer therapy. Methods: We retrospectively reviewed children aged 14 years or younger who received cancer-directed therapy at a tertiary cancer center in Kerala, India, from January through December 2022. ILI was defined using World Health Organization criteria. Patient time was calculated from the exact time receiving active therapy and under observation. Episode-level logistic and Poisson generalized estimating-equation models accounted for repeated episodes within children. Results: Seventy-nine of 110 children (71.8%) developed 209 ILI episodes over 68.95 patient-years, corresponding to 3.03 episodes per patient-year (95% CI: 2.63-3.47). The median age of affected children was 4 years (IQR=2 to 6), and 62 (78.5%) had hematological malignancies. Seventy-four episodes (35.4%) were managed as inpatients, including 30 hospital-onset episodes; 44 of 179 community-onset episodes (24.6%) resulted in admission. Lower respiratory tract infection occurred in 33 episodes (15.8%). Severe pneumonia occurred during 9 episodes involving 7 children; all required intensive care. Two children developed multiple organ dysfunction syndrome, required ventilation, and died, corresponding to an ILI-related mortality of 2.5% among affected children. Chemotherapy was delayed in 64 episodes (30.6%); among 62 episodes with assessable duration, the median delay was 7 days (IQR=4 to 7). Viral testing was performed in 26 episodes (12.4%); SARS-CoV-2 was detected in 9 of 24 rapid antigen tests (37.5%). Younger age independently predicted inpatient management (adjusted odds ratio=0.78 per year; 95% CI: 0.65-0.93; P =0.006). Female sex (adjusted incidence rate ratio=0.77; 95% CI: 0.63-0.94; P =0.012) and solid-tumor diagnosis (adjusted incidence rate ratio=0.71; 95% CI: 0.57-0.89; P =0.003) were associated with shorter inpatient duration. Conclusions: Syndromic ILI was frequent and was associated with inpatient care, severe complications, and chemotherapy interruption. Younger children had higher odds of inpatient management. Limited pathogen testing restricts etiological interpretation and supports improved access to respiratory diagnostics, risk-adapted antimicrobial stewardship, and age- and treatment-appropriate vaccination against preventable respiratory infections.