Study on clinical features and epidemiology among 10 patients had avian influenza A who treated in hospital in Ho Chi Minh City and Ha Noi 12/2003 and 1/2004, 13,7 mean age. In all patients, the diagnosis of influenza A (H5N1) was confirmed by means of viral culture or reverse transcriptase polymerase chain reaction (RT-PCR) with primers specific for H5 and N1. None of the 10 patients had pre-existing medical conditions. Nine patients had a clear history of direct contact with poultry. All patients had fever, respiratory symptoms and clinically significant lymphopenia. The medium platelet count was 75.500/mm3. Seven patients had diarrhea. In all patients, there were marked abnormalities on chest radiography. There was no definitive evidence of human to human transmission, eight patients died
Influenza A Virus, H5N1 Subtype ; Influenza in Birds ; epidemiology

At the end of 2003 and early 2004, an epidemic of avian influenza with 10 cases and 7 deaths occurred in the North of Vietnam, a subtype H5N1 (A/H5N1) has been identified. The prevalence of total infection with epidemic syndrome in the whole area at the same time was 0.1%, the prevalence infected cases of death was very high (70%). The epidemic was widely distributed in 7 provinces and the highest number of cases was observed in the forth week by the onset of the first case. Sick hens were the evidence of causes. There was not direct infection from human to human. However, there were two case-clusters that happened in the same family, this may be a suggestion of biological and familial factors associated with the susceptibility to the causal virus A/H5N1
Epidemiology ; Influenza A Virus ; H5N1 Subtype ; Influenza in Birds

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.

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

From February 2013, a novel avian influenza A H7N9 virus causing human infection with fatal outcomes has been identified in eastern China. This avian influenza A H7N9 virus is a triple reassortant of viruses that are avian-origin only and it is low pathogenic in poultry. Several characteristic amino acid mutations in HA and PB2 polymerase subunit (including G186V, Q226L and E627K substitution) have been found through sequence analysis, and these mutations probably facilitate binding to human-type receptors and efficient replication in mammals. Other mutations in NA, M2 and NS genes were also found. Although sustained human-to-human transmission has not been conclusively established, limited human-to-human transmission of the H7N9 virus remains possible. Intensified surveillance for the H7N9 virus in humans and animals is needed to answer questions about the viral origin, spread and potential threat.
Animals ; Birds ; virology ; China ; epidemiology ; Humans ; Influenza A virus ; genetics ; Influenza in Birds ; virology ; Influenza, Human ; transmission ; virology ; Mutation

Animals ; Birds ; virology ; China ; epidemiology ; Humans ; Influenza A virus ; classification ; pathogenicity ; Influenza Vaccines ; Influenza in Birds ; epidemiology ; prevention & control ; Influenza, Human ; epidemiology ; prevention & control

Objective: To analyze the characteristics of low pathogenic H3, H4 and H6 subtypes of avian influenza viruses in environment related avian influenza viruses in China from 2014 to 2021. Methods: Surveillance sites were located in 31 provinces, autonomous region and municipalities to collect environmental samples related to avian influenza, detect the nucleic acid detection of influenza A virus, isolate virus, deeply sequence, analyze pathogenicity related molecular sites, and determine the distribution and variation characteristics of common H3, H4 and H6 subtypes of avian influenza virus in different regions, places and sample types. Results: A total of 388 645 samples were collected. The positive rate of low pathogenic H3 (0.56‰) and H6 (0.53‰) was higher than that of H4 (0.09‰). The positive rate of H4 subtype virus in live poultry market was higher than that in other places, and the difference was statistically significant. The positive rate of H3 and H6 subtypes in sewage samples was higher than that in other samples, and the difference was statistically significant. The positive rate of H3, H4 and H6 viruses in the south was higher than that in the north, and the difference was statistically significant. December was the most active time for virus. The analysis of pathogenicity related molecular sites showed that H3, H4 and H6 subtypes of viruses combined with avian influenza virus receptors, and some gene sites related to increased pathogenicity had mutations. Conclusion: The H3, H4 and H6 subtypes of low pathogenic avian influenza viruses have a high isolation positive rate in the live poultry market and sewage. The distribution of the three subtypes of viruses has obvious regional and seasonal characteristics, and the genetic characteristics still show the feature of low pathogenic avian influenza.
Humans ; Animals ; Influenza in Birds/epidemiology* ; Sewage ; Phylogeny ; Influenza A virus/genetics* ; Poultry ; China/epidemiology*

The circulation and infection of avian influenza virus (AIV) in zoos and backyard flocks has not been systematically investigated. In the present study, we surveyed the birds including those in live bird markets (LBMs) and evaluated co-circulation of AIVs among them. Overall, 26 H9N2 AIVs and one H6N2 AIV were isolated from backyard flocks and LBMs, but no AIVs were isolated from zoo birds. Genetic analysis of the HA and NA genes indicated that most of the H9N2 AIVs showed higher similarities to AIVs circulating in domestic poultry than to those in wild birds, while the H6N2 AIV isolate from an LBM did to AIVs circulating in migratory wild birds. In serological tests, 15% (391/2619) of the collected sera tested positive for AIVs by competitive-ELISA. Among them, 34% (131/391) of the sera tested positive for AIV H9 antigen by HI test, but only one zoo sample was H9 positive. Although AIVs were not isolated from zoo birds, the serological results indicated that infection of AIVs might occur in zoos. It was also confirmed that H9N2 AIVs continue to circulate and evolve between backyard flocks and LBMs. Therefore, continuous surveillance and monitoring of these flocks should be conducted to control further epidemics.
Animals ; Birds ; Influenza in Birds ; Korea ; Molecular Epidemiology ; Poultry ; Serologic Tests ; Viruses

Human, birds and other mammals can be infected by avian influenza A (H5N1) virus. Bird infections spread among continents in the last 2 years. Human infections become endemic in certain areas, characterized with young patients and high mortality. An unprecedented epizootic avian influenza A (H5N1) virus that is highly pathogenic has crossed the species barrier in Asia to cause many human fatalities and poses an increasing pandemic threat. This summary describes the features of human infection with influenza A (H5N1) in epidemiology and etiology and reviews recommendations for prevention.
Animals ; Birds ; China ; epidemiology ; Humans ; Indonesia ; epidemiology ; Influenza A Virus, H5N1 Subtype ; pathogenicity ; Influenza in Birds ; prevention & control ; transmission ; Influenza, Human ; epidemiology ; prevention & control ; transmission

Avian influenza viruses (AIV) have been isolated from a wide range of domestic and wild birds. Wild birds, predominantly ducks, geese and gulls form the reservoir of AIV in nature. The viruses in wild bird populations are a potential source of widespread infections in poultry. Active surveillance for AIV infection provides information regarding AIV distribution, and global AIV surveillance can play a key role in the early recognition of highly pathogenic avian influenza (HPAI). Since 2003 in Korea, there have been four H5N1 HPAI outbreaks caused by clade 2.5, 2.2 and 2.3.2. Therefore, improvement of AIV surveillance strategy is required to detect HPAI viruses effectively. This article deals with the major events establishing the role of wild birds in the natural history of influenza in Korea. We highlighted the need for continuous surveillance in wild birds and characterization of these viruses to understand AIV epidemiology and host ecology in Korea.
Animals ; Birds* ; Charadriiformes ; Disease Outbreaks ; Ducks ; Ecology ; Epidemiology ; Geese ; Influenza in Birds* ; Influenza, Human ; Korea* ; Natural History ; Poultry ; Viruses*