ABSTRACT
Objective To investigate the spatial and temporal distribution of highly pathogenic avian influenza H5N1 based on Geography Information System (GIS),and to learn the mechanism of the occurrence and spread of H5N1.Methods A total of 2 069 officially confirmed cases of H5N1 outbreak reported to WHO and World Organization for Animal Health (OIE)from 2003 to 2012 were analyzed using a GIS based approach.Hot spot analysis (Getis-Ord Gi*)was used in the spatial and temporal analysis.Results From 2003 to 2012,2 069 cases of H5N1 outbreak was reported in Vietnam (1 055),Bangladesh (528)and Indonesia (209).The most of the outbreaks were reported in Ganges Delta,Mekong Delta,areas around Dacca and West Java.The occurrence,spread and distribution pattern of the disease varied within different spatial scale,and the epidemic showed a bipolar distribution in Vietnam,aradial distribution in Bangladesh and a shrinking pattern in Indonesia.Conclusion Highly pathogenic avian influenza H5N1 was first emerged in city and then spread through poultry trading or transportation,and finally caused epidemic in regions with high density poultry and intensive agriculture.Hot spot analysis had a great application value in disease surveillance and early warning.
ABSTRACT
Objective To investigate the source of the first human case of avian influenza A (H5N1) infection in Beijing. Methods Interviewing the relatives of the case and other key persons, collecting and detecting samples of related biological, epidemiological and environmental data of the case were conducted. Later, the infection source was thoroughly investigated. Results The case ever contacted a slaughtered duck 5 days prior to the onset of illness, and the duck was bought from a stall of a wet market in Yanjiao area of Hebei province. Ten environmental samples were collected in this stall and the neighboring stall of the market. Another 6 samples were tested positive for H5N1 virus by PCR method, with 5 virus strains isolated. The whole-genome sequencing indicated that the amino acid homology between the H5N1 virus strains from the environment and the virus isolated from the case reached 99.8%-100%. Conclusion From both epidemiological and virological evidence, it was proved that the first human case of avian influenza A (H5N1) infection in Beijing was infected by a duck that carrying H5N1 virus the case contacted 5 days proceeding the onset of illness.