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Two variant strains of the Avian Influenza A(H7N9) viruses causing human infections were identified in China

2017-02-20

In January 2017, the gene sequencing analysis of the viruses isolated from two human A(H7N9) cases by Guangdong Provincial Center for Disease Control and Prevention showed amino acid insertion mutations at the cleavage site of the haemagglutinin (HA) molecule, which have been confirmed by the Chinese National Influenza Center of Chinese Center for Disease Control and Prevention (China CDC).

 

Based on experts assessments of China CDC, and a discussion among the experts of China CDC and Ministry of Agriculture, we considered the amino acid insertion mutations at the cleavage site of the HA indicated that the A(H7N9) virus had mutated into highly pathogenic virus to poultry. According to the analysis results of genome sequences, any mutation that might enhance the human adaptation, virulence and the capacity of human-to-human transmission was not yet found in these two variant strains.

 

The two human cases both had poultry exposure history, and in these poultry that they exposed, sick and dead poultries were subsequently discovered. So far, one case had recovered and another one is still under treatment. After two weeks of medical observation, all the 105 close contacts of these two cases did not appear the clinical symptoms such as fever, cough, etc.

 

A(H7N9) virus is a subtype of avian influenza A virus, and one of its important characteristics is prone to genetic reassortment and mutation. Since some mutations might enhance the human adaptation, virulence or the capacity of human-to-human transmission, the mutation of A(H7N9) has always been a great international concern.

 

As far as we known, viruses with similar variation had been isolated from four poultry specimens of Guangdong Province by the laboratory of agricultural department. In order to enhance the surveillance of A(H7N9) virus and timely detect any potential mutation of A(H7N9) virus, the National Health and Family Planning Commission and the Ministry of Agriculture will work together on the research of the source and the impact of the mutant virus .

 

The above results have been reported to the World Health Organization (WHO).

 

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