Monitoring Avian Influenza A(H7N9) Virus through National Influenza-like Illness Surveillance, China

Xu, Chen; Havers, Fiona; Wang, Lijie; Chen, Tao; Shi, Jianzhong; Wang, Dayang; Yang, Jing; Yang, Liu; Widdowson, Marc‐Alain; Shu, Yuelong

doi:10.3201/eid1908.130622

Cited by 14 publications

(14 citation statements)

References 9 publications

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“…Laboratory confirmation of a small number of A(H7N9) virus infections with mild to moderate disease is suggestive of a larger number of mild to moderate cases. 8 In addition, as of May 24, 17 A(H7N9) cases are still in hospital, and the current A(H7N9) outbreak may yet not have ended which could lead to some bias in the follow-up data. Second, our estimates of the incubation period are based on a subset of 32 cases with information on single or repeated exposures, while accurate and complete information on exposures can be difficult to ascertain.…”

Section: Discussionmentioning

confidence: 99%

Comparative epidemiology of human infections with avian influenza A H7N9 and H5N1 viruses in China: a population-based study of laboratory-confirmed cases

et al. 2013

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Background The novel influenza A(H7N9) virus recently emerged, while influenza A(H5N1) virus has infected humans since 2003 in mainland China. Both infections are thought to be predominantly zoonotic. We compared the epidemiologic characteristics of the complete series of laboratory-confirmed cases of both viruses in mainland China to date. Methods An integrated database was constructed with information on demographic, epidemiological, and clinical variables of laboratory-confirmed A(H7N9) and A(H5N1) cases that were reported to the Chinese Center for Disease Control and Prevention up to May 24, 2013. We described disease occurrence by age, sex and geography and estimated key epidemiologic parameters. Findings Among 130 and 43 patients with confirmed A(H7N9) and A(H5N1) respectively, the median ages were 62y and 26y. In urban areas, 74% of cases of both viruses were male whereas in rural areas the proportions were 62% for A(H7N9) and 33% for A(H5N1). Among cases of A(H7N9) and A(H5N1), 75% and 71% reported recent exposure to poultry. The mean incubation periods of A(H7N9) and A(H5N1) were 3.1 and 3.3 days, respectively. On average, 21 and 18 contacts were traced for each A(H7N9) case in urban and rural areas respectively; compared to 90 and 63 for A(H5N1). The hospitalization fatality risk was 35% (95% CI: 25%, 44%) for A(H7N9) and 70% (95% CI: 56%, 83%) for A(H5N1). Interpretation The sex ratios in urban compared to rural cases are consistent with poultry exposure driving the risk of infection. However the difference in susceptibility to serious illness with the two different viruses remains unexplained, given that most A(H7N9) cases were in older adults while most A(H5N1) cases were in younger individuals. Funding Ministry of Science and Technology, China; Research Fund for the Control of Infectious Disease and University Grants Committee, Hong Kong Special Administrative Region, China; and the US National Institutes of Health.

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Section: Discussionmentioning

confidence: 99%

Comparative epidemiology of human infections with avian influenza A H7N9 and H5N1 viruses in China: a population-based study of laboratory-confirmed cases

et al. 2013

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“…The data suggests that severity of H7N9 virus infection severity increases with increasing age. 44 The risk factors associated with moderate-to-severe ARDS tended to manifest at the age of 65 years or older in the form of coexisting medical conditions, lymphocyte count,1000 cells/mm 3 , aspartate aminotransferase level.40 U/l, creatine kinase level.200 U/l and.3 days time from symptom onset to initiation of antiviral therapy. 35 …”

Section: Severity Of H7n9 Infectionmentioning

confidence: 99%

Global alert to avian influenza virus infection: From H5N1 to H7N9

Poovorawan

Pyungporn

Prachayangprecha

et al. 2013

Pathogens and Global Health

120

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Outbreak of a novel influenza virus is usually triggered by mutational change due to the process known as 'antigenic shift' or re-assortment process that allows animal-to-human or avian-to-human transmission. Birds are a natural reservoir for the influenza virus, and subtypes H5, H7, and H9 have all caused outbreaks of avian influenza in human populations. An especially notorious strain is the HPAI influenza virus H5N1, which has a mortality rate of approximately 60% and which has resulted in numerous hospitalizations, deaths, and significant economic loss. In March 2013, in Eastern China, there was an outbreak of the novel H7N9 influenza virus, which although less pathogenic in avian species, resulted in 131 confirmed cases and 36 deaths in humans over a two-month span. The rapid outbreak of this virus caused global concern but resulted in international cooperation to control the outbreak. Furthermore, cooperation led to valuable research-sharing including genome sequencing of the virus, the development of rapid and specific diagnosis, specimen sharing for future studies, and vaccine development. Although a H7N9 pandemic in the human population is possible due to its rapid transmissibility and extensive surveillance, the closure of the live-bird market will help mitigate the possibility of another H7N9 outbreak. In addition, further research into the source of the outbreak, pathogenicity of the virus, and the development of specific and sensitive detection assays will be essential for controlling and preparing for future H7N9 outbreaks.

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“…H7N9 infection causes severe illness, including pneumonia and ARDS [,2]. A recent epidemiological survey seeking influenza-like illness caused by avian influenza A[H7N9] confirms the preferential targeting of the elderly by this virus, since it found no evidence of widespread mild disease in young people in the Chinese provinces with confirmed human cases of infection [3]. The virus preferentially targets elderly people with comorbidities due probably to the weak immune status of this demographic.…”

mentioning

confidence: 97%

Weakened immunity in aged hosts with comorbidities as a risk factor for the emergence of influenza A H7N9 mutants

Bermejo-Martín

Almansa

Lejarazu

2013

J Infect Dev Ctries

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Monitoring Avian Influenza A(H7N9) Virus through National Influenza-like Illness Surveillance, China

Cited by 14 publications

References 9 publications

Comparative epidemiology of human infections with avian influenza A H7N9 and H5N1 viruses in China: a population-based study of laboratory-confirmed cases

Comparative epidemiology of human infections with avian influenza A H7N9 and H5N1 viruses in China: a population-based study of laboratory-confirmed cases

Global alert to avian influenza virus infection: From H5N1 to H7N9

Weakened immunity in aged hosts with comorbidities as a risk factor for the emergence of influenza A H7N9 mutants

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