Chinese CDC Study Finds High Risk Features Of H7N9 Virus

A new study from the Chinese CDC suggests that the H7N9 influenza A virus possesses a suite of biological features that may be a serious threat to humans.

AsianScientist (Jul. 5, 2013) – A new study from the Chinese Center for Disease Control and Prevention in Beijing, China suggests that the H7N9 influenza A virus possesses a suite of biological features that may be a serious threat to humans.

To date, a total of 132 confirmed cases and 39 deaths have been reported to the World Health Organization, with most patients suffering from severe pneumonia and acute respiratory distress syndrome.

Although the immediate threat from the H7N9 avian influenza virus is over, the presence of a natural reservoir and the disease severity highlight the need to evaluate its risk on human public health and to understand the possible pathogenesis mechanism.

The new report published in Nature this week by Yuelong Shu and colleagues show that, unlike H5N1 and H1N1 influenza viruses, the H7N9 virus binds to avian (α2,3-linked sialic acid) and human-type (α2,6-linked sialic acid) receptors.

It infects and replicates within cells of the human trachea and lungs, reaching even those cells at the furthermost tips of the respiratory tree.

Most patients infected with the virus become severely ill, and acute serum samples from H7N9-infected patients show an unusually high level of inflammatory and immune cells, referred to as a ‘cytokine storm,’ which may contribute to symptom severity.

This dual receptor binding and high growth may make the H7N9 virus more likely to be transmitted from birds to humans. However, the decreased ability of H7N9 to replicate in the trachea compared to the lungs may relate to its inefficient human-to-human transmission.

Further, the authors note their concern that the human population is naive to the H7N9 virus, and that the current seasonal vaccine offers no protection, highlighting the importance of undertaking intensive surveillance for this virus.

The article can be found at: Zhou J et al. (2013) Biological features of novel avian influenza A (H7N9) virus.

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Source: NPG; Photo: Augapfel/Flickr/CC.
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