Is H7N9 Spreading from Human to Human in China?

[AlaskaDenise]

Re: Is H7N9 Spreading from Human to Human in China?

snip


"Scientists have in fact detected influenza viruses frozen in the ice and mud of lakes in Alaska, Siberia and elsewhere. These Arctic lakes are the summer grounds for ducks that migrate to China, Southern Asia, Europe and North America."

http://www.wired.com/wiredscience/2009/05/iceplague/

Those lakes thaw every summer anyhow - no global warming needed. That's why the ducks go there regularly. What is new is the accelerated thawing of glaciers which feed the lakes, shores, etc. The other change due to global warming is that some of these same lakes are being drained of all their water, since the permafrost under them is thawing - it only takes one small spot to drain the lake, just like pulling the plug in a bathtub. In 2006, they estimated there were thousands of such lakes lost to climate warming. It translates into migratory bird populations concentrated in fewer lakes, which could accelerate their "sharing" of AI genes. This will be an added stressor for birds that don't normally share lakes during - like loons & trumpeter swans, etc. I found some nesting swans "sharing" some back lakes last summer while kayaking thru lake grasses.

.

 

[JJackson]

Re: Is H7N9 Spreading from Human to Human in China?

Recreating a viral sequence using RT-PCR is one thing, viable viruses quite another. Producing sufficient viral load to naturally induce an infection from an archaic ice sample is, in my opinion, extremely unlikely. Producing one from short term freezing might work. A much more plausible explanation for the reintroduction of H1N1 in the seventies, with identical sequences to the pre 1957 pandemic, is lab escape.

 

[gsgs]

Re: Is H7N9 Spreading from Human to Human in China?

freezing and thawing is not good for the virus' transmissiability
said one study, afair. We don't really see the sequences that are conserved
for winter or even for several years.

The slow evolution of avian flu in China 1975-2000 (also H3N8 in Alaska ?)
in some strains was in warmer regions. Maybe prolonged existence in water
between the infection cycles, I don't know.
Or it existed in some organs or organelles for some time without replicating.
But this is an exception, not what we usually see.
I.e. not in poultry or mammals or bats or geese or gulls

 

[curiosity]

Re: Is H7N9 Spreading from Human to Human in China?

Shanghai is not reporting as many cases - a result of the wet market closures and culling? This might be a good sign that the disease is NOT transmitting efficiently between humans, right? Instead, perhaps transmitting only in rare, very close contact situations?

 

[Giuseppe]

Re: Is H7N9 Spreading from Human to Human in China?

It would be nice to know how things are going on the ground. It seems that Keiji Fukuda acknowledged today in Shanghai the lack of an ongoing h2h spread but it is also a question of foreign relations, diplomacy.

Some clues may come from recent human isolates sequences: if among these isolates persist the great diversity seen until now - as underlined by M. Koopmans - it could be a sign of a birds-to-human spread instead h2h.

But until we will have the most recent sequences it will take several weeks and in this timeframe all things can happen.

 

[gsgs]

Re: Is H7N9 Spreading from Human to Human in China?

diversity is small, consistent with a start in Jan. or Feb.
occasional reassortments grasp 1 or 2 segments from H9N2
(-->comes from poultry, we won't expect reassortment with H9N2
in humans)
no signs of h2h, afaict

occasionally there are some more mutations, presumably due to
prolonged disease or sequencing errors.
As in S1, which others attribute to a 2nd introduction or had let
me give a start date of ~1 year ago before. But this is not seen
in other sequences, it's just S1.
Diversity in NA is bigger than in other segments (~2-3 fold),
I assume it's because current H7N9 is not yet quite happy with its NA (?!)

 

[curiosity]

Re: Is H7N9 Spreading from Human to Human in China?

Given that many detected bird to human avian influenza viruses have caused occasional H2H incidents without ongoing transmission, the hope is, of course, that this situation will be similar and that those possible cases are limited and dead ended.

I have read the genetic discussions (most of which are far beyond my intellect) and their reference to an unstable(?) virus - and - I have questions...

Are unstable genetic characteristics common in all recently re-assorted viruses?
In avian influenzas?
In human influenzas?
How does the H7N9 virus stability compare to other instances of avian influenza and their infection of humans? particularly with second/third generation H2H incidents?

 

[Giuseppe]

Re: Is H7N9 Spreading from Human to Human in China?

We lack of most recent isolates to say whether some genetic markers have become fixed, suggesting a common human source of infection.

But clearly there are too many unknowns about the extent of this endemic to draw any conclusion.

There is also a lack for sentinel surveillance for influenza-like illness in general. We cannot say whether among primary care doctors in China people presenting with non-specific upper respiratory tract symptoms have been swabbed and subsequently tested for the H7N9 virus.

The SARI surveillance is the main source of positive H7N9 cases and could not represent the real pattern of disease severity or complete clinical spectrum of illness.

Without these pivotal data the risk assessment is risky for all, WHO notwithstanding weak tone.

H3N2v in the US last year spreaded back and forth in various separated states without creating a great fanfare despite its acquisition of an internal gene segment directly from H1pdm09.

These viruses may circulate unnoticed among animals and human for years but only recently detected through greatly improved bio-molecular probes not available in the past.

We can hardly figure the 1957 H2N2 virus in the earlier stage of its spread now. At the time it was discovered only after community outbreaks. But if they would have had current PCR high throughput Platform, how earlier the virus may have had detected?