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H7N9 Avian Influenza Outbreak in China

Apr 23, 2013

As previously reported, the Rosselkhoznadzor is monitoring the situation concerning spread of H7N9 influenza in China. H7N9 has not been detected in the territory of Russia; Russia does not import live animals or poultry products from China.

In this context and due to incoming requests the Rosselkhoznadzor deems it appropriate to inform that H7N9 influenza has so far been isolated only in affected birds. Moreover the disease outbreaks were registered only in the Netherlands, Italy, Canada, Mexico, Great Britain, Japan and the USA. Only one human death case in the Netherlands was reported. But the Rosselkhoznadzor virologists predicted new outbreaks of the disease in Southeast Asia, particularly in China.

First outbreaks in China were reported on March 31, current year. Up to this moment 91 H7N9 cases have been confirmed in humans in the territory of China, i.e. 32 cases in Shanghai, 22 cases in Jiangsu, 30 in Zhejiang, 3 cases in Anhui and 3 cases in Hainan and one case in Beijing. 17 affected humans died. Three cases in family members were registered and that may be indicative of the fact that virus acquired the ability to transmit from humans to humans.

Molecular analysis of H7N9 AIV isolated from the first human cases in China showed that the virus structure is characteristic for a virus infecting birds. Moreover the analysis revealed the evidence of virus adaptation in mammal organism. This evidence includes the ability to bind to mammal cell receptors and growth at temperatures typical for mammal's body temperature, which is lower than avian body temperature. Besides human adaptation marker PB2 E627K was detected.

Significant peculiarities in temporal dynamics of diseases induced by H7 virus were noted. 10 years ago the H7N7 outbreak (which is structurally related to H7N9) affected 255 poultry farms in the Netherlands resulting in culling of 30 million birds. 453 persons who worked on poultry farms had mild influenza. The major symptom of human influenza in China now is a severe pneumonia. Laboratory tests showed that H7N9 virus is sensitive to neuraminidase inhibitors, such as oseltamivir and zanamivir. Prevention vaccine against H7N9 virus was not developed. At the same time avian infection (chickens, geese, ducks and doves) is asymptomatic or mild.

H7N9 has never been isolated in the territory of the Russian Federation. The Rosselkhoznadzor is monitoring the situation.

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