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. 2013 Nov;19(11):1784-90.
doi: 10.3201/eid1911.130865.

Use of national pneumonia surveillance to describe influenza A(H7N9) virus epidemiology, China, 2004-2013

Nijuan Xiang, Fiona Havers, Tao Chen, Ying Song, Wenxiao Tu, Leilei Li, Yang Cao, Bo Liu, Lei Zhou, Ling Meng, Zhiheng Hong, Rui Wang, Yan Niu, Jianyi Yao, Kaiju Liao, Lianmei Jin, Yanping Zhang, Qun Li, Marc-Alain Widdowson, Zijian Feng

Use of national pneumonia surveillance to describe influenza A(H7N9) virus epidemiology, China, 2004-2013

Nijuan Xiang et al. Emerg Infect Dis. 2013 Nov.

Abstract

In mainland China, most avian influenza A(H7N9) cases in the spring of 2013 were reported through the pneumonia of unknown etiology (PUE) surveillance system. To understand the role of possible underreporting and surveillance bias in assessing the epidemiology of subtype H7N9 cases and the effect of live-poultry market closures, we examined all PUE cases reported from 2004 through May 3, 2013. Historically, the PUE system was underused, reporting was inconsistent, and PUE reporting was biased toward A(H7N9)-affected provinces, with sparse data from unaffected provinces; however, we found no evidence that the older ages of persons with A(H7N9) resulted from surveillance bias. The absolute number and the proportion of PUE cases confirmed to be A(H7N9) declined after live-poultry market closures (p<0.001), indicating that market closures might have positively affected outbreak control. In China, PUE surveillance needs to be improved.

Keywords: China; epidemiology; influenza; influenza A(H7N9) virus; influenza virus; pneumonia surveillance; viruses.

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Figures

Figure 1
Figure 1
Number of reported PUE cases, mainland China, January 2004–May 2013. SARS, severe acute respiratory syndromes; H5N1, human infection with avian influenza A(H5N1) virus; PUE, pneumonia of unknown etiology.
Figure 2
Figure 2
Number of PUE cases, confirmed influenza A(H7N9) cases reported, and cumulative affected provinces or municipalities, mainland China, March 30–May 3, 2013. *Confirmed A(H7N9) cases reported through the PUE surveillance system. †Cumulative affected provinces/municipalities reporting cases through the PUE system. ‡Cases reported through PUE system. PUE, pneumonia of unknown etiology.
Figure 3
Figure 3
Reported PUE cases and confirmed influenza A(H7N9) cases reported before and after LPM closures, Shanghai (A), Nanjing (B), and Hangzhou (C), mainland China, March 30–May 3, 2013. PUE, pneumonia of unknown etiology; LPM, live-poultry market; J, January; M, May; S, September.
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