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Online Discussion: Tracking new emerging diseases and the next pandemic; Now tracking the Aussie Flu.

Tiny genetic change lets bird flu leap to humans

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carbon20 View Drop Down
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    Posted: March 21 2017 at 2:07pm

Tiny genetic change lets bird flu leap to humans

Poultry, ChinaImage copyrightGETTY IMAGESImage captionAt least six provinces have reported human cases of H7N9 influenza this year, according to Chinese state media

A change in just a single genetic "letter" of the flu virus allows bird flu to pass to humans, according to scientists.

Monitoring birds for viruses that carry the change could provide early warning of risk to people, they say.

Researchers at the University of Hong Kong studied a strain of bird flu that has caused human cases in China for several years.

Birds carry many flu viruses, but only a few strains can cause human disease.

H7N9 is a strain of bird flu that has caused more than 1,000 infections in people in China, according to the World Health Organization.

Most cases are linked to contact with infected poultry or live poultry markets.

The change in a single nucleotide (a building block of RNA) allows the H7N9 virus to infect human cells as well as birds, say Prof Honglin Chen and colleagues.

They say there is "strong interest in understanding the mechanism underpinning the ability of this virus to cause human infections and identification of residues that support replication in mammalians cells is important for surveillance of circulating strains."

Flare-up

Dr Derek Gatherer, an expert on viruses at Lancaster University, UK, says more surveillance of bird flu viruses is needed.

"The recent flare-up of H7N9 bird flu in China has been the cause of some concern this winter, and the demonstration that the new replicative efficiency mutation is present in this strain is not good news," he told BBC News.

"Also, the observation that this mutation has been present in other bird flu subtypes like H9N2 and spreading slowly for over 15 years shows that H7N9 isn't the only kind of bird flu that is potentially a pandemic risk for humans.

"We need to maintain a broader surveillance of bird flu to identify which strains have this mutation."

The research, published in the journal, Nature Communications, will help scientists understand more about how bird flu viruses adapt to infect humans.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote CRS, DrPH Quote  Post ReplyReply Direct Link To This Post Posted: March 21 2017 at 5:17pm
^Thanks, Carbon20, good stuff!  The proverbial Sword of Damocles!! 

The change in a single nucleotide (a building block of RNA) allows the H7N9 virus to infect human cells as well as birds, say Prof Honglin Chen and colleagues.  


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Eight Quote  Post ReplyReply Direct Link To This Post Posted: March 21 2017 at 5:44pm
A single nucleotide change is nothing for influenza. 

In any case, I managed to find the actual paper in question. The above article annoyingly makes no mention of it. What makes this mutation worrying is twofold: 

1) Of course, the fact that it's a single nucleotide change means that any given infected cell likely, on average, would create such a mutant. 

2) This mutation does not prevent the mutant from replicating in birds. We're aware of many such mutations that allow for zoonosis to occur or enhance the likelihood of such an event, but some make the virus less fit in bird populations. As a result, they appear and flit out of existence. Mutations that maintain fitness in birds are cause for concern.

http://www.nature.com/articles/ncomms14751
Such a beautiful number, eight.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote arirish Quote  Post ReplyReply Direct Link To This Post Posted: March 22 2017 at 12:25pm
HK researchers identify mutation in H7N9 virus

Source: Xinhua | March 22, 2017, Wednesday

A mutation in H7N9 avian flu virus that can enhance the ability of the virus to infect humans was identified by researchers from the University of Hong Kong, which made the finding public on Wednesday.

The research team from the university's State Key Laboratory for Emerging Infectious Diseases of and the department of Microbiology analyzed the H7N9 virus genome collected from 2013 onwards and revealed that efficient infection of both avian and human cells by H7N9 viruses is supported by a unique nucleotide substitution (NS-G540A) in NS segment, where the mutation is located within a previously undefined exonic splicing enhancer (ESE).

Mutation in ESE identified in the viral genome of H7N9 virus enhances the ability of virus replication in mammalian cells. It is notable that human infections with H10N8 and H5N6 subtype avian influenza viruses contain the same mutation in the viral genome.

This mutated nucleotide emerged in early 2000 in H9N2 strains and has since spread in avian influenza viruses, becoming the dominant genotype among avian influenza viruses from 2012 onwards, the researchers said.

Viruses that can infect humans are normally refrained from replication and transmission in avian cells. Yet the mutation in H7N9 virus can enhance the virus replication in mammalian and human cells.

The mutation enables H7N9 virus to possess the cross-species transmission ability to infect humans. The primed condition of NS-G540A among H7N9 virus enhances replication ability in mammalian hosts and facilitates viral acquisition of other adaptive mutations during virus infection, which enables H7N9 virus to infect humans more effectively than other avian influenza viruses.

"This study provides a plausible mechanism to explain the molecular properties which allows H7N9 virus to infect humans while retaining the ability to circulate in avian species," Chen Honglin, Professor of the university's Faculty of Medicine said.

The finding provides an important biomarker for monitoring the emergence and transmission of avian influenza viruses in humans and preventing human-to-human infection of the viruses, Chen said, adding the mutation can also serve as a novel target of anti-influenza drug development.

The research has been published in the international journal Nature Communications.

http://www.shanghaidaily.com/nation/HK-researchers-identify-mutation-in-H7N9-virus/shdaily.shtml
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