PLEASE HELP - bird flu. significance of this diagram

http://www.newscientist.com/data/images/archive/2533/25331502.jpg

This is what I am using as a base for by biology AS coursework..

I am doing an issue report with my aspects as 1) causes and treatments of bird flu and 2)effects of bird flu on humans.

Firstly I wasnt really sure whether this could really come under causes of bird flu in humans? Could it?

Also I don't understand what the significance of the diagram is other than that the virus has the ability to hijack the cells defenses and is therefore dangerous. Could anyone help me out?

Reply 1

Revenged

15

katwilliams88

http://www.newscientist.com/data/images/archive/2533/25331502.jpg

This is what I am using as a base for by biology AS coursework..

I am doing an issue report with my aspects as 1) causes and treatments of bird flu and 2)effects of bird flu on humans.

Firstly I wasnt really sure whether this could really come under causes of bird flu in humans? Could it?

Also I don't understand what the significance of the diagram is other than that the virus has the ability to hijack the cells defenses and is therefore dangerous. Could anyone help me out?

I can't read anything that's in that link but sure i can help...

All influenza viruses are catagoried be common factors:

Influenza is a RNA virus (viruses are either DNA or RNA)

Influenza is a segmented virus - which means that it has many RNA strands forming it's nucleic acid

Influenza is also an enveloped virus...

On this envelope there is a two protein common proteins - one of which is called neuraminidase, which is used in uncoating process of the influeza virus...

You may hear the term "H5N1", this refers to the proteins of the envelope of the influenza virus - haemaglutinin 5, neuraminidase 1

Uncoating occurs after influenza virus has entered the cell and involves the release of nucleic acid from the envelope - which one of the diagram is showing - and it's caused by neuraminidase somehow... This is necessary to prevent the replication of the virus...

Tamiflu, which you may of heard of, is an anti-viral agent since it prevents the replication of the virus. It is a neuraminidase inhibitor and so prevents the uncoating of the influenza virus and so stops replication of the virus.

Another anti-viral agent is amantadine, which prevents the release of the virus from the cell. Though it is ineffective against avian flu.

The immune system defence against virus is may not be AS level material but essentially in involves getting protein synthesised by the virus and puts this protein on the membrane of the cell... T cells (cytotoxic) then recognise this on the cell and they then destroy the virus infected cell...

This occurs by the MHC-class I molecules that are present on all cells and the pathway for this is called the endogenous pathway - but these are just details you probably don't need to know...

As for some of the questions you ask, I don't really know the answers to...

Though it is important to realise that the risk of bird flu is that it may combine with human flu to form a deadly, easily spread virus (bird flu is deadly but is not easily spread) by a process called "antigenic shift"

Hope that was helpful, Revenged

Reply 2

Helenia

20

The diagram is about viral evasion mechanisms and how it manages to infect cells and escape the immune system. It doesn't really come under "Causes" of the disease itself, but could be mentioned as a side note on why it is highly dangerous.

Reply 3

MadNatSci

12

By "causes of bird flu in humans" do you mean how it can be transmitted to humans from birds directly? If so you could talk about the fact that it mentions H5 has mutated so it can bind to both. (Though actually I'd not heard this and I'm not entirely sure this isn't NewScientist oversimplifying: my reasoning is that the birds' type of sialic acid is found lower down humans' respiratory tract* and there have been papers published recently to this effect. Let me email my lecturer to find out if there's any truth in the 'mutated to bind both types' assertion - I'll get back to you ASAP.)

*you can use this to explain how it can transmit to humans. A nice deep breath could carry the virions far enough down so they can grab the right kind of sialic acid and wham! Massive damage to lungs. Interestingly the bird type of sialic acid is also found in the eye: remember the farm worker who got conjunctivitis after dealing with H7 infected chickens the other day?

Reply 4

MadNatSci

12

Nicky's lecturer

I'm not sure what info the New Scientist piece is based on. As far
as I'm aware, MOST H5 HAs from the dreaded H5N1 viruses prefer 2,3 to
2,6. But, it's not absolute - there will still be some binding to
2,6. There have been a few isolates of H5N1 from people (Turkey was
the latest) with mutations (relative to the pool of most H5s) that
would be predicted to alter receptor specificity. IIRC (I don't
think this is published yet, just something I heard at a meeting last
month), these mutations leave the HA in a half-way situation, perhaps
what the NS piece is referring to - able to bind both, but neither as
well as is perhaps optimal.

Yes, you would think this sort of think would make the virus even
more of a threat and the WHO are looking out for this sort of thing
in the surveillance programme. Perhaps there's something else needed
to really make the virus go pandemic, or perhaps we've just been
lucky so far and although it could have transmitted, it didn't for
reasons of chance.

So I suspect the diagram is oversimplifying, to be honest, or at least it's sticking its neck out quite a lot!

I'm not sure if any of this was what you were after - if it was, hope it helped, and if it wasn't I hope you find it interesting anyway :wink:

edited to add: in case you were wondering, 2,3 sialic acid is the type you normally get in birds and 2,6 is the type most commonly found in humans.

PLEASE HELP - bird flu. significance of this diagram

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