H7N9: A virus worth watching

H7N9

Influenza A H7N9 as viewed through an electron microscope. Both filaments and spheres are observed in this photo.” class /> Influenza A H7N9 as viewed through an electron microscope. Both filaments and spheres are observed in this photo.

Thanks to the two Virology Hangouts on Air that Scott Lewis and I hosted (“Going Viral” – SciSunHOA from 28 April, 2013 and “Ferreting out the Truth”: H5N1 #SciSun Panel Discussion), I have viruses on my mind (in a good way!). So it was with interest that I read about the recent outbreaks of H7N9 in China. If you want a nice primer on why influenza strains have these letters to their name, read +Deeksha Tare’s post here (which explains the significance of Hemagglutinin and Neuraminidase).

H7N9 is an animal influenza A virus that has crossed the species barrier to infect humans. The first human infection was reported in China two months ago, and the latest WHO report confirms a total of 108 cases and 22 deaths thus far. The virus has now spread beyond mainland China as a case has been reported in Taiwan.

• One predecessor, the H5N1 strain, generated a lot of alarm and controversy (see our Hangout on Air coming up on Sunday about this topic), but fortunately H5N1 has not adapted to humans, and person to person transmission is rare. Another predecessor H1N1 successfully adapted to humans and caused a pandemic in 2009 (aka ‘swine flu’).

• It is currently unclear if H7N9 will cause a similar pandemic or if it will fizzle out. It has been reported that some of the proteins found on the surface of the virus are similar to other bird flu viruses that cause only mild symptoms in birds. The implication is that the virus could spread silently within domestic and wild bird populations without displaying any obvious symptoms. Therefore, the human infections are the warning ‘red flags’. If H7N9 were to stably adapt to humans, it would probably meet with little or no human immunity. There is currently no vaccine available for H7N9.

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