Abstract
We collected 2768 Influenza-like illness emergency public health incidents from April 1, 2005 to November 30, 2013reported in the Emergency Public Reporting System. After screening by strict inclusion and exclusion criteria, there were 613 outbreaks analyzed with susceptible–exposed–infectious/asymptomatic–removed model in order to estimate the proportion of asymptomatic individuals (p) and the effective reproduction number (Rt). The relation between Rt and viral subtypes, regions, outbreak sites, populations, and seasons were analyzed. The mean values of p of different subtypes ranged from 0.09 to 0.15, but could be as high as up to 0.94. Different subtypes, provinces, regions, and sites of outbreak had statistically significantly different Rt. In particular, the southern region also manifested different Rt by affected population size and seasonality. Our results provide China and also the rest of the world a reference to understand characteristics of transmission and develop prevention and control strategies.
Highlights
Influenza is a respiratory infectious disease which can result in annual infection of 5–15% of the population, leading to 250,000 and 500,000 deaths[1]
The criteria for an influenza outbreak was defined as !30 Influenza-like illness (ILI) occurring in the same school, preschool, or other collective organization within 1 week [10], with laboratory-confirmed influenza viruses through virus isolation or real-time reverse transcriptase polymerase chain reaction (RT-PCR) analysis
From April 1, 2005 to November 30, 2013, 2768 ILI emergency public health incidents in China were reported in Emergency Public Reporting System (EPRS)
Summary
Influenza is a respiratory infectious disease which can result in annual infection of 5–15% of the population, leading to 250,000 and 500,000 deaths[1]. Surveillance of the disease agents at the human and animal interface facilitates early detection of influenza transmission. Numerous outbreaks of influenza/ILI are reported every year throughout China. From April 1, 2005 to November 30, 2013, there were 2,768 influenza/Influenza-like illness (ILI) outbreaks recorded in the Emergency Public Reporting System (EPRS).There are two systems in China for influenza surveillance: one is National Public Health Information System and the other is the PLOS ONE | DOI:10.1371/journal.pone.0166180. The two systems are linked, such that the influenza outbreak report in the first system is directly synchronized to the second system. Before November 2012 it is mandatory to report any incident with more than 30 cases of ILI weekly in the same unit (equivalent to class IV public health emergency). This study adopted the definition of 30 cases for analysis
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