Use of National Pneumonia Surveillance to Describe Influenza A(H7N9) Virus Epidemiology, China, 2004–2013

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.

Identifying areas with a high risk of human infection with the avian influenza A (H7N9) virus in East Asia

“…However, our results suggest hypotheses that should be tested more specifically in future studies. The significant association between LBM density and H7N9 cases in our model provides further support for the hypothesis that LBMs are an important source of H7N9 transmission to humans 3, 10, 28 . A previous study found a tight coupling between climatic variables and seasonal influenza in humans in Hong Kong 29 .…”

“…Closing LBMs appears to be an effective approach for eradicating or reducing H7N9 infections in humans 10 . In poultry, policies to control H7N9 include culling on positive farms and vaccination.…”

“…However, in April and December 2013, two patients were hospitalized in Taiwan after being infected with H7N9 in Jiangsu 7, 8 , and an additional patient was hospitalized in Malaysia in February 2014 following infection in Guangdong 9 , highlighting the potential for long distance spread via air travel. After peaking in March and early April 2013, the number of new cases decreased significantly in late April and May following the closure of LBMs in the affected areas in early April and no cases were reported in June 10 . The sharp reduction in cases could be due to many reasons, including the fact that seasonal and avian influenza in humans historically reach low levels during the summer in China 11 .…”

H7N9: Preparing for the Unexpected in Influenza

“…Almost all cases were hospitalized, and 158 (36%) died. The majority of cases [309 [19][20][21][22][23][24][25], and a more equal sex distribution (56% male cases) (27). The reasons for the predominance of older male cases are not understood but have been attributed to cultural practices in which older men may be more likely to shop at LPMs.…”

“…Surveillance systems for outpatient influenza-like illness and pneumonia of unknown etiology, established following the emergence of SARS and H5N1, were enhanced to greatly increase the numbers of specimens tested throughout China (23,24). Clinician and public awareness for symptoms and testing was raised through traditional and social media such as Weibo, the Chinese equivalent to Twitter (25).…”