Bird Flu cross over

[jake-the-peg]

It's being reported in a few areas of the media that a human-bird flu cross over variant could arise if somebody was simultaneously infected by both strains.

Can somebody with a better grasp of biology than me say if this is possible or just reporters getting the wrong end of the stick?

After all viruses like flu don't reproduce sexually! do they? 

[Wavy Davy]

I'm not a microbiologist so don't quote me, but...

A virus is basically a piece of genetic material (DNA or RNA) in a protein box. It does not perform many of the normal functions of life and so is not even generally considered as a living entity. So we basically have some complex chemicals capable of hijacking the machinery of the living cells of their hosts for the purpose of making copies of themselves.

If someone has both viruses then you have the mass manufacture of two separate DNA or RNA sequences, possibly in the same or adjacent cells. DNA and RNA are long chains that are easily damaged - in a sausage factory you get bits of sausage all over the floor.

With the mass manufacture taking place amongst bits of RNA/DNA debris, it's quite conceivable that a bit of debris genetic material gets incorporated into the manufacture of another sequence.

So, as you point out, no sexual reproduction takes place, but mixing of genetic matter can easily occur. If this by chance makes the new sequence more robust or faster reproducing then a new, more dangerous virus strain may result.

[KT84]

The way i understand that it may turn in to a virus that can be passed from person to person is if it mutates (i had not herd of the way your describing jake).  Basically as davy says when dna and rna are coppied (cant remember all the ins and outs of this process its been 3 years since i did a-level biology, or any biology for that matter) sometimes the process can go wrong and the copy changes, maybe only one part of the chaing will change but it can make a difference.

[scubadiver]

Wavy Davy is correct- in essence you would get "genetic mixing" of material from both human and avian flu virions if they co-infected the same cell. This would lead to an "antigenic shift" - which is in essence a radical change of the genetic make-up of the human flu virus, into something that there would be no levels of background immunity- hence a potential pandemic.

Also, to confuse the issue even further, pig cells can host both human and avian forms of the flu virus (they are often known as "mixing vessels" for flu). So if a pig were to be co-infected with both flu strains the same thing could happen.

[Davis McBain]

http://www.hpa.org.uk/infections/topics_az/avianinfluenz a/avianflufaq.htm

[Peter Pedant]

Information between viruses can be done by, transduction, transfection and recombination.

Dont ask me anymore I havent done virology for 35 years.

Jumping species barriers for avian flu is difficult we know this because Romania is full of dying swans etc but NOT full of dying Romanians.

Once it does - you would expect it to propagate. I thought they were worried about straightforward mutation (RNA reproduction is NOT very efficient and therefore mutation is common) more than anything else