[paul.fr]

There are many forms of Influenza, i think these differ by the amount of their hemagluttinin H or the neuraminidase N. my spelling could be wrong here.

So why is the varient H5N1, the one we are most scared of?
is it because this is the mostlikely strain to mutate with the human flu? and would it be most likely to mutate with Influenza A, B or c?

Paul

[another_someone]

Most diseases live in balance with their host.  If a disease kills off all its host species, then it deprives itself of the needs for its own existence, so over time, the disease causing agent learns to cause no more damage to its host than is necessary (and its host similarly learns to tolerate the disease), so both continue to survive.

The problem is when a disease moves from one host to a new host species, and has not formed this balancing act.  This is what happened with HIV, which was relatively innocuous as SIV, but when it jumped over to humans, it was in a new environment where it was not in a state of balance with its host (no doubt, over time, it will form such a balance, after a substantial number of humans have been killed off).  H5N1 is seen as a candidate for jumping that species barrier, and entering into a new environment where it has not yet found a balance.  It is still highly speculative as to whether it will successfully jump that barrier (although the flu virus is well known for jumping between species), but nonetheless people do panic over the possibility it might do so.

[paul.fr]

H5N1 is seen as a candidate for jumping that species barrier, and entering into a new environment where it has not yet found a balance.  It is still highly speculative as to whether it will successfully jump that barrier (although the flu virus is well known for jumping between species), but nonetheless people do panic over the possibility it might do so.

but why is the H5N1 strain, of all strains, the one to cause the most concern? Why not H5N2? This is also an avian flu virus and has infected at least 90 people, of which at least one died.

Paul

[another_someone]

Maybe not totally satisfactory as an answer:

http://www.who.int/csr/don/2004_01_15/en/

[h3]Why H5N1 is of particular concern[/h3]
Of the 15 avian influenza virus subtypes, H5N1 is of particular concern for several reasons. H5N1 mutates rapidly and has a documented propensity to acquire genes from viruses infecting other animal species. Its ability to cause severe disease in humans has now been documented on two occasions. In addition, laboratory studies have demonstrated that isolates from this virus have a high pathogenicity and can cause severe disease in humans. Birds that survive infection excrete virus for at least 10 days, orally and in faeces, thus facilitating further spread at live poultry markets and by migratory birds.

The epidemic of highly pathogenic avian influenza caused by H5N1, which began in mid-December 2003 in the Republic of Korea and is now being seen in other Asian countries, is therefore of particular public health concern. H5N1 variants demonstrated a capacity to directly infect humans in 1997, and have done so again in Viet Nam in January 2004. The spread of infection in birds increases the opportunities for direct infection of humans. If more humans become infected over time, the likelihood also increases that humans, if concurrently infected with human and avian influenza strains, could serve as the “mixing vessel” for the emergence of a novel subtype with sufficient human genes to be easily transmitted from person to person. Such an event would mark the start of an influenza pandemic.

http://en.wikipedia.org/wiki/H5N1

Due to the high lethality and virulence of HPAI A(H5N1), its endemic presence, its increasingly large host reservoir, and its significant ongoing mutations, the H5N1 virus is the world's largest current pandemic threat, and billions of dollars are being spent researching H5N1 and preparing for a potential influenza pandemic

It seems that H5N2 is considered a high risk to birds, but seems only to be a marginal risk to humans (not zero risk, but only slight risk by comparison to H5N1 - although the economic risks with H5N2 are substantial because of the risk to poultry).

[paul.fr]

Thanks another_someone,for the links and info.

Paul

[DrN]

I live in the outer restriction zone for the Bernard Matthews Suffolk H5N1 outbreak! I'm not allowed to move my chickens on the roads, or to feed them outdoors.

[paul.fr]

How do the restrictions compare to the bse outbreak?

[DrN]

barely noticable! not too many people keep chickens any more, and the farms keep them in sheds mainly. I've not been past the turkey farm lately, but I expect it to be fairly quiet. cows on the other hand live in fields, that have public footpaths going through them. much greater chance of spreading an infection.

my nan used to have chickens in the back garden, it used to be relatively common. I think I might even remember them vaaguely. i guess things would have been a bit different with H5N1 back then.

[Mjhavok]

Influenza, or "the flu," is caused by an RNA virus occurring in eight segments. Each segment is bounded by protein, and the eight segments are enclosed in an envelope containing spikes. Two antigens called hemagglutinin (H) and neuraminidase (N) are found in the spikes. The H and N antigens vary among influenza viruses and account for the many influenza strains in our society.

The changes occurring in the H and N antigens are examples of anitgenic shift. Antigenic shift results in varying strains of influenza viruses and is responsible for the yearly outbreaks of influenza. For example, the body man develop antibodies against a certain strain in one year, only to have a new strain occur the following year. Since antibodies produced the previous year are ineffective against this strain, the patient suffers another attack of the disease.

Viruses are named according to which H and N antigens are present: for example H3 and N2. In addition, influenza viruses are classified as types A, B and C. Thus, an influenza virus may be designated A(H3N2).

The avian influenza virus is A(H5N1).

[paul.fr]

barely noticable! not too many people keep chickens any more, and the farms keep them in sheds mainly. I've not been past the turkey farm lately, but I expect it to be fairly quiet. cows on the other hand live in fields, that have public footpaths going through them. much greater chance of spreading an infection.

my nan used to have chickens in the back garden, it used to be relatively common. I think I might even remember them vaaguely. i guess things would have been a bit different with H5N1 back then.

i actually meant, how do the restrictios compare. is there a big quarantine area? do you have to disinfect cars and footware, that toye of thing...sorry for my original vagueness fishy.

[Mjhavok]

Transmissible spongiform encephalopathy diseases (also known as prion diseases) are caused by a unique type of infectious agent called a prion, an abnormally structured form of a protein found in the brain. Other prion diseases include Gerstmann-Sträussler-Scheinker syndrome (GSS), fatal familial insomnia (FFI) and kuru in humans, as well as bovine spongiform encephalopathy (BSE) commonly known as mad cow disease, chronic wasting disease (CWD), and scrapie in sheep.


I think restriction would and should be a lot more extensive for a viral outbreak. Especially H5N1.

[paul.fr]

I think restriction would and should be a lot more extensive for a viral outbreak. Especially H5N1.

I was thinking the same, but there has been to my knowledge no mention of this in the news.

as a side note, do you think we should see Mr Matthews feeding his excellent (sic) chicken products to his children! The same as , was it gummer?, the minister did when the bse outbreak occured?

[Mjhavok]

lol I hope not.

[paul.fr]

Put your chicken (surely money) where your mouth is Bernard.

[another_someone]

I think restriction would and should be a lot more extensive for a viral outbreak. Especially H5N1.

I think it is all too easy to panic, and overreact to these things.

Sometimes, the reaction to a problem does more damage than the problem itself.

While it is true that the initial reaction to BSE was underplayed, the ultimate reaction (considerring that, despite all the panic, only around 170 human infections have been identified) was grossly overplayed.  As for the panic surrounding the foot and mouth outbreak a few years ago...


Ofcourse we want to minimise risk, but risk also has to be traded against having a continued viable farming industry, and if we destroy our farming industry, then we will end up losing control over the risks we take with imported food.

[Mjhavok]

Don't we have better quality beef now because of the BSE scare?

[another_someone]

Don't we have better quality beef now because of the BSE scare?

Not sure about that - it certainly is more expensive, and I believe we have fewer producers who now dominate the market (ofcourse, saying that this is so, and saying that there is a provable causal link, are two different things).

What certainly has happened is that the changes that came in after BSE meant that most abattoirs went out of business, and cattle could not be slaughtered near the farms the were in, which required much greater movement of cattle around the country, and this contributed to the outbreak of foot and mouth a few years later.