Transmission Dynamics, Border Entry Screening, and School Holidays during the 2009 Influenza A (H1N1) Pandemic, China - Vol. 18 No. 5 - May 2012 - Emerging Infectious Disease journal - CDC

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Transmission Dynamics, Border Entry Screening, and School Holidays during the 2009 Influenza A (H1N1) Pandemic, China - Vol. 18 No. 5 - May 2012 - Emerging Infectious Disease journal - CDC

Table of Contents
Volume 18, Number 5–May 2012

Volume 18, Number 5—May 2012

Research

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

Article Contents

• Methods
• Results
• Discussion
• Acknowledgments
• References
• Figure 1
• Figure 2
• Figure 3
• Figure 4
• Figure 5
• Table 1
• Table 2
• Table 3
• Technical Appendix  [967 KB - 13 pages]
• Suggested Citation

Hongjie Yu¹, Simon Cauchemez¹, 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 , and Zijian Feng

Author affiliations: Chinese Center for Disease Control and Prevention, Beijing, People’s Republic of China (H. Yu, L. Zhou, L. Feng, N. Xiang, J. Zheng, M. Ye, Y. Huai, Q. Liao, Z. Peng, Y. Feng, H. Jiang, W. Yang, Y. Wang, Z. Feng); Imperial College London, London, United Kingdom (S. Cauchemez, C.A. Donnelly, N.M. Ferguson)

Suggested citation for this article

Abstract

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.

Pandemic influenza A (H1N1) 2009, hereafter referred to as A(H1N1)pdm09, spread rapidly, resulting in millions of cases and ≈18,000 deaths in ≈200 countries (1). On August 10, 2010, the World Health Organization (WHO) declared that the world had entered the postpandemic period (2). Much has been published about the epidemiology of the pandemic in Western countries (3–9), but far less has been published about the experience of a large and diverse country, such as the People’s Republic of China. In addition, although many countries adopted so-called early containment strategies, data on their effectiveness are rare (7,10,11).
In response to the evolving global spread of A(H1N1)pdm09 virus infection, China established national surveillance on April 30, 2009. Initially, the country implemented an aggressive containment strategy based on the national pandemic preparedness plan, including isolation of all suspected case-patients in designated hospitals, contact tracing, medical observation of persons exposed to patients with confirmed cases, and border entry screening (Technical Appendix  [PDF - 967 KB - 13 pages]). On May 11, the first case of A(H1N1)pdm09 in mainland China was identified in a traveler returning from the United States (12). We report the transmission patterns of A(H1N1)pdm09 in China from that time through November 2009 and analyze the effectiveness of border entry screening and holiday-related school closures on transmission using multiple data sources from surveillance systems and specific investigations.