BACKGROUNDIn March 2013, human cases of infection with a novel A (H7N9) influenza virus emerged in China. The epidemic spread quickly and as of 6 May 2013, there were 129 confirmed cases. The purpose of this study was to analyze the epidemiology of the confirmed cases, determine the impacts of bird migration and temperature changes on the H7N9 epidemic, predict the future trends of the epidemic, explore the response patterns of the government and propose preventive suggestions.

METHODSThe geographic, temporal and population distribution of all cases reported up to 6 May 2013 were described from available records. Risk assessment standard was established by analysing the temperature and relative humidity records during the period of extensive outbreak in three epidemic regions in eastern China, including Shanghai, Zhejiang and Jiangsu provinces. Risk assessment maps were created by combining the bird migration routes in eastern China with the monthly average temperatures from May 1993 to December 2012 nationwide.

RESULTSAmong the confirmed cases, there were more men than women, and 50.4% were elderly adults (age >61 years). The major demographic groups were retirees and farmers. The temperature on the days of disease onset was concentrated in the range of 9°C-19°C; we defined 9°C-19°C as the high-risk temperature range, 0°C-9°C or 19°C-25°C as medium risk and <0°C or >25°C as low risk. The relative humidity on the days of disease onset ranged widely from 25% to 99%, but did not correlate with the incidence of infection. Based on the temperature analysis and the eastern bird migration routes, we predicted that after May, the high-risk region would move to the northeast and inland, while after September, it would move back to north China.

CONCLUSIONSTemperature and bird migration strongly influence the spread of the H7N9 virus. In order to control the H7N9 epidemic effectively, Chinese authorities should strengthen the surveillance of migrating birds, increase poultry and environmental sampling, improve live poultry selling and husbandry patterns and move from a "passive response pattern" to an "active response pattern" in focused preventive measures.

China ; epidemiology ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Influenza, Human ; epidemiology ; virology

Antiviral Agents ; therapeutic use ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Influenza, Human ; drug therapy ; epidemiology ; virology

Adolescent ; Humans ; Influenza A Virus, H7N9 Subtype ; immunology ; pathogenicity ; Lymphopenia ; immunology ; microbiology ; Male ; T-Lymphocytes ; metabolism

Animals ; Birds ; China ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Influenza in Birds ; epidemiology ; virology ; Influenza, Human ; epidemiology ; virology

Adult ; Aged ; Brugada Syndrome ; diagnosis ; virology ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Influenza, Human ; diagnosis ; virology ; Male ; Middle Aged

Antiviral Agents ; therapeutic use ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Influenza, Human ; diagnosis ; diet therapy ; Middle Aged

Herpes Zoster Oticus ; diagnosis ; virology ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Magnetic Resonance Imaging ; Male ; Middle Aged

Animals ; Antiviral Agents ; therapeutic use ; Birds ; China ; Humans ; Influenza A Virus, H7N9 Subtype ; pathogenicity ; Influenza in Birds ; transmission ; Influenza, Human ; drug therapy ; epidemiology ; transmission ; Oseltamivir ; therapeutic use

Objective: To investigate the infection pattern and etiological characteristics of a case of human infection with highly pathogenic avian influenza A (H7N9) virus and provide evidence for the prevention and control of human infection with highly pathogenic avian influenza virus. Methods: Epidemiological investigation was conducted to explore the case's exposure history, infection route and disease progression. Samples collected from the patient, environments and poultry were tested by using real time reverse transcriptase-polymerase chain reaction (RT-PCR). Virus isolation, genome sequencing and phylogenetic analysis were conducted for positive samples. Results: The case had no live poultry contact history, but had a history of pulled chicken processing without taking protection measure in an unventilated kitchen before the onset. Samples collected from the patient's lower respiratory tract, the remaining frozen chicken meat and the live poultry market were all influenza A (H7N9) virus positive. The isolated viruses from these positive samples were highly homogenous. An insertion which lead to the addition of multiple basic amino acid residues (PEVPKRKRTAR/GL) was found at the HA cleavage site, suggesting that this virus might be highly pathogenic. Conclusions: Live poultry processing without protection measure is an important infection mode of "poultry to human" transmission of avian influenza viruses. Due to the limitation of protection measures in live poultry markets in Guangzhou, it is necessary to promote the standardized large scale poultry farming, the complete restriction of live poultry sales and centralized poultry slaughtering as well as ice fresh sale.
Animals ; Chickens ; China ; Commerce ; Humans ; Influenza A Virus, H7N9 Subtype/pathogenicity* ; Influenza in Birds/virology* ; Influenza, Human/virology* ; Phylogeny ; Poultry/virology* ; Real-Time Polymerase Chain Reaction ; Zoonoses