Transmission Dynamics, Border Entry Screening, and School Holidays during the 2009 Influenza A (H1N1) Pandemic, China

• Main Authors: Enfu Chen, Simon Cauchemez, Christl A. Donnelly, Lei Zhou, Luzhao Feng, Nijuan Xiang, Jiandong Zheng, Min Ye, Yang Huai, Qiaohong Liao, Zhibin Peng, Yunxia Feng, Hui Jiang, Weizhong Yang, Yu Wang, Neil M. Ferguson, Zijian Feng
• Format: Article
• Language: English
• Published: Centers for Disease Control and Prevention 2012-05-01
• Series: Emerging Infectious Diseases
• Subjects: transmission; school closure; border screening; influenza A; pandemic (H1N1) 2009; China
• Online Access: https://wwwnc.cdc.gov/eid/article/18/5/11-0356_article

Pandemic influenza A (H1N1) 2009 virus spread rapidly around the world in 2009. We used multiple data sources from surveillance systems and specific investigations to characterize the transmission patterns of this virus in China during May–November 2009 and analyze the effectiveness of border entry screening and holiday-related school closures on transmission. In China, age distribution and transmission dynamic characteristics were similar to those in Northern Hemisphere temperate countries. The epidemic was focused in children, with an effective reproduction number of ≈1.2–1.3. The 8 days of national holidays in October reduced the effective reproduction number by 37% (95% credible interval 28%–45%) and increased underreporting by ≈20%–30%. Border entry screening detected at most 37% of international travel–related cases, with most (89%) persons identified as having fever at time of entry. These findings suggest that border entry screening was unlikely to have delayed spread in China by >4 days.