Monitoring OTC Drug Sales for Early Detection of Respiratory Infectious Disease Outbreaks

Junjie Li¹CHEN WU¹Kui Liu¹Qinbao Lu¹Xinyi Wang¹Zheyuan Ding¹Tianying Fu¹Xuefeng Jiang^2*Haocheng Wu^1*

• ¹Zhejiang Center for Disease Control and Prevention (Zhejiang CDC), Hangzhou, China
• ²Pinghu City Center for Diseases Control and Prevention, Shaanxi Provincial Center for Disease Control and Prevention, Xi'an, China

In recent years, over-the-counter (OTC) drug sales have emerged as a novel indicator for symptom monitoring, attracting widespread attention in public health research globally. This study conducted weekly monitoring of five OTC drug categories related to fever respiratory system diagnostic cluster (FRSDC) — antitussive/expectorant drugs, cold medications, antibiotics, pungent and cool exterior-relieving agents, and influenza medicine — in Pinghu City, Zhejiang Province, from 2022 to 2024. Concurrently, weekly FRSDC cases from Pinghu First People's Hospital were collected. Spearman correlation analysis was used to quantify associations between OTC sales and FRSDC cases, while decision tree models evaluated the reliability of OTC data for early prediction of FRSDC trends. Results showed significant positive correlations between all five OTC drugs and FRSDC cases, with synchronous seasonal peaks in winter and spring (Spearman's correlation coefficients ranged from 0.36 to 0.80, all P value ≤ 0.0001). Even when OTC drug sales preceded FRSDC cases by one or two weeks, strong correlations persisted (Spearman's correlation coefficients ranged from 0.28 to 0.79, P value ≤ 0.0001). Decision tree analysis revealed that combining antitussive/expectorant drugs and influenza medications effectively predicted FRSDC epidemics with 83.33% accuracy (adjusted P value < 0.05). These findings suggest that monitoring OTC drug sales may serve as a useful early warning indicator for FRSDC, potentially aiding public health response and resource planning.