There certainly have been OTHER strains of bird flu here. That's well
known.
The differences with this one are that:
1. When humans do get it* this type of bird flu causes what is called a
cytokine storm. This is a major immune system response which several
types of illnesses can create (infections with sepsis are probably the
most common cause in humans in recent decades), and it is THE biggest
danger with the strains of this current more dangerous avian influenza
(at least for those who do not have TB or some other problems). It is
this type of response which causes illnesses that generate it to be more
of a hazard for those who are young or in their primes. Why? Because
their immune systems are stronger. That is why the bird flu that hit
in the 19-teens took so many people in their childhood into their 30s
or so, rather than being more dangerous for older people as usually
happens with influenza.
(It is this type of immune system response which is thought to be
happening with DIM in ferrets, BTW. There is the open question if
ferrets whose immune systems do not over-respond get whatever causes
DIM but do not suffer the over-response so get past it.)
2. This particular version of bird flu which already has at least 2
clades** which humans have caught from direct contact with the infected
birds changes easily. Clades are a type of taxonomic division system.
As you see, this particular virus mutates more easily that is typical.
That increases the risk of mutations which could make it directly
contagious. Influenzas are not strictly living because they use the DNA
of their hosts for certain functions such as reproduction. What this
means is that the more humans who catch the strain, the more chances
there are of the strain picking up human genetic material which can
change it enough to be contagious among humans. In some cases this
could just be generalized to infected mammals.
3. There is currently a large human population with very suppressed
immune systems in the world. AIDS iis not the only concern but it is
a big one for several reasons:
A. It is more common in the same areas where there are poor controls of
infected poultry.
B. Such severely immune compromised people will not be inclined to have
cytokine storms so they do not die off rapidly
C. Because of the immune system lack of response the infection can last
longer in them. The combinations of B and C mean that this creates a
situation with a higher chance of the mutations needed to create a
casually contagious influenza. Because this virus is so easily mutated
that gives more chance for genetic drift (slow change in a virus --
like gradualism in paleotology) or genetic shift (more rapid and larger
change in a virus -- like punctualism in paleontology).
Here is why this particular bird flu is not currently directly
transmitted by among mammals:
1. So far the "pegs" it has that fit into cell receptors are only the
right shape to fit cells deep in the lungs. This location does not cause
the dislodging effects (coughing and sneezing, or easy moving to the
hands) that an upper respiratory infection causes. If it mutates enough
to fit upper respiratory cells (most influenzas fit in receptors that are
in the nose, sinuses, throat, and brochioles) then those transmission
routes can be created.
2. The virus does not at this point also does not have a certain type
of enzyme change that would be needed for easy reproduction in humans
(probably at this stage in mammals in general). That change also needs
to happen for it to be a serious threat to humans.
*Ditto some other mammals, including ferrets, cats, etc. who develop
cytokine storms. Dogs who ate infected birds are known to have gotten
it from antibodies present but vet care wasn't available in that area of
Asia so until more data comes from Europe we won't know if it presents
more mildly in them, which still means that they get this influenza. I
do not know if pigs have been checked for this one, but have not heard
of that, yet. Pigs are among the mammals that often get strains of
influenza.
**The majority of the viruses [of H5N1], including all the human cases,
belonged to genotype Z. Now there are two clades of the Z genotype.
There were also small numbers of viruses in birds that were genotype V or
W or recently identified genotype G. (from a Reuters virology article)
BTW, this strain so far is very heat sensitive so cooking at normal
poultry cooking temperatures kills it, but how one becomes exposed from
the infected birds is still unknown, and the response to an infected
poultry flock is to destroy the flock.
Guano (bird waste) is being studied to see if it can transmit the strain.
There are recommendations to seal-in poultry farms and zoo birds. This
is to reduce the risk of them being exposed to wild carriers of the
virus. That is why so many zoos are now building shelters around the
outside bird cages.
Most of the virologists who are experts on this think that with this
particular strain it is *not a matter of if* it will infect humans
casually, but *a matter of when* it will acquire the needed mutations to
do so. If we get really lucky, the mutated virus won't cause cytokine
storms, but don't count on that at all, please. It pays to learn how to
work from home when possible, to have stockpiles of essentials such as
meds and foods (says she who still needs to do that far better) etc.
for when it finally flares. Schools are being encouraged to explore
distance teaching with family playing a large role for when this happens.
It would be a good thing for parents to acquire books and other learning
materials such as word games, puzzles, documentary and classical DVDs and
videos, learning materials that are housed by your own computers, and so
on. Remember that this also means that the personnel keeping such things
as essential Internet nodes and some utilities, etc. might also at times
wind up seriously understaffed so may not be reliable. Expect some
possible times when "cabin fever" (a term for being in home so long that
a person craves getting out and having other contacts) would actually be
a good thing... Expect, too, that once casual transmission among humans
occurs that transportation could be curtailed. This information is all
available in the major health sites of world, regional, and national
organizations. Please, check those for further information.
[Posted in FML issue 5194]
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