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