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**Catbird** · April 30, 2013, 12:19 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Originally posted by Giuseppe Michieli View Post

...And if there are so many cases, why does the overall situation not point toward a widespread workpalces abseenteism or school closures, mass burials?

Because if the cfr is really 20% and the iceberg is growing, than we must have mass burials or cremations...

How do you know that there isn't an increase in absenteeism in work places or schools? The only information source for such statistics is the Chinese government. The rest of the world is only informed about such matters via state controlled agencies and media. People who aren't Chinese citizens who live there, and who may have access to such information even if it's only anecdotal, are constrained by the knowledge that they are guests of a government who can tell them to leave at any time.

Objective, verifiable facts about what impact this outbreak is having on China's social or economic activities are simply not available. The lack of reports about absenteeism doesn't necessarily mean that there hasn't been an increase. It just means that we don't know if there has been an increase or not.

**Laidback Al** · April 30, 2013, 12:25 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Originally posted by Pathfinder View Post

Vincent Racaniello:

. . . . What also tempers my concern about these H7N9 viruses is the fact that the last influenza pandemic (H1N1 virus) took place in 2009. No influenza pandemics in modern history are known to have taken place 4 years apart, although only 11 years separated the 1957 (H2N2) and 1968 (H3N2) pandemics. I suppose that is not much consolation, as there are always exceptions, especially when it comes to viruses."
...

I find this comment surprising from Dr. Racaniello. It seems to based on a presumption that because it hasn't happen yet, it won't happen in the future. While it is true that pandemics have a cyclical periodicity based on modern recorded history, the cause for the cyclical occurrence is unclear.

In an article by Taubenberger and Morens, Pandemic influenza – including a risk assessment of H5N1, they state:

Application of the criteria listed above to the available historical information suggests that there may have been at least 13 pandemics over the past 500 years (1509 to 2009), or approximately one pandemic every 38 years. These pandemics may not have occurred randomly. Whether or not there has been clustering of pandemics, there is evidence that some (but not all) pandemics have been followed by periods of high respiratory disease activity, which were associated with large outbreaks and high mortality, over a number of years. It may thus be helpful to think not only about pandemics as events that occur at specific points in time, but to consider also the occurrence of ‘pandemic eras’.

For example, the 90 years since 1918 can be said to comprise a pandemic era, because all of the influenza A viruses circulating since that time, up to the present, are descendants of the 1918 virus, and because seasonal influenza activity has been detected continuously during that period. Yet clearly in that interval there have been three (depending on how one defines the H1N1 recurrence in 1977, see below) or four pandemics.

We could be entering a new pandemic era if A(H7N9) or A(H5N1) becomes a pandemic strain. If so, there is no reason to believe that there needs to be a 38-year hiatus between pandemic eras.

**curiosity** · April 30, 2013, 03:03 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Originally posted by Pathfinder View Post

Vincent Racaniello:

"What also tempers my concern about these H7N9 viruses is the fact that the last influenza pandemic (H1N1 virus) took place in 2009. No influenza pandemics in modern history are known to have taken place 4 years apart, although only 11 years separated the 1957 (H2N2) and 1968 (H3N2) pandemics. I suppose that is not much consolation, as there are always exceptions, especially when it comes to viruses."
...
http://www.virology.ws/2013/04/16/av...(virology+blog

A few thoughts about "pandemic" intervals:

Without knowing a re-assorted virus created illness in 2009 - would it have been historically referenced as a Pandemic? Was the disease severe enough to have created so much interest the historians would have documented as such? Compared to diseases that routinely took out populations every year (particularly those under 5), IMO, H1N1pdm might have been noticed as a seasonal flu.

Population now is different than past pandemic events - perhaps increasing population = decreasing pandemic intervals = natural homeostasis, aka, balancing out the population.

Host competition between influenza viruses? - we know, we have seen, that although people are susceptible to more than one influenza virus - there is typically a dominant strain. Why don't susceptible people get sick twice in a year with BOTH circulating strains?

What if the population susceptibility to seasonal flu strains decreases so much because of consistent runs of the same virus that there are not enough people ill with seasonal influenza and a new strain now has the ability to get into the population without being the "fittest" , dominant virus? (What did China's flu season look like this year?)

**Giuseppe** · April 30, 2013, 03:10 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

I think that H1pdm09 - although mild in its overall clinical presentation - was a game-changer: after its emersion, a lot of new reassortants appeared in different places, and one of the most fit was surely the H3N2v, that is circulating currently in the US pigs population.

H1pdm09 is parenting H1, H3 swine viruses and it is not said that it could interact with other flu strains too.

China has seen a lot of H1pdm09 acitivity this year, for this reason I suggest a comparison between H1pdm09 circulation areas and H7N9 emersion.

Conversely, in the US H3N2 caused a severe season for not fully understood reasons.

Further, the H3N2 was not replaced by H1pdm09 at all.

In some weeks, Southern China regions should see the start of summer flu season: what will be the interference between H3, H1pdm09 and the new H7N9?

**curiosity** · April 30, 2013, 03:53 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Originally posted by Giuseppe Michieli View Post

Further, the H3N2 was not replaced by H1pdm09 at all.

I agree, H1pdm09 was a game changer, and in the long term, did not replace H3N2 - except for one season.

After the first season, both viruses, in North America specifically, were detected frequently. Even this year, although H3N2 dominated, H1pdm09 was still detected with frequency.

**JimO** · April 30, 2013, 03:56 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Originally posted by curiosity View Post

A few thoughts about "pandemic" intervals:

Without knowing a re-assorted virus created illness in 2009 - would it have been historically referenced as a Pandemic? Was the disease severe enough to have created so much interest the historians would have documented as such? Compared to diseases that routinely took out populations every year (particularly those under 5), IMO, H1N1pdm might have been noticed as a seasonal flu.

Population now is different than past pandemic events - perhaps increasing population = decreasing pandemic intervals = natural homeostasis, aka, balancing out the population.

Host competition between influenza viruses? - we know, we have seen, that although people are susceptible to more than one influenza virus - there is typically a dominant strain. Why don't susceptible people get sick twice in a year with BOTH circulating strains?

What if the population susceptibility to seasonal flu strains decreases so much because of consistent runs of the same virus that there are not enough people ill with seasonal influenza and a new strain now has the ability to get into the population without being the "fittest" , dominant virus? (What did China's flu season look like this year?)

All excellent points. You are probably right about calling the pdmH1N1 a true pandemic if compared with criteria used in decades past. It might have been viewed as a bad flu season, but might not have been recognized as a pandemic.

**AlaskaDenise** · April 30, 2013, 06:31 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Originally posted by sharon sanders View Post

Isn't it really odd that Ministry of Agriculture scientists have published a paper about a disease which is NOT in animals (except a couple of pigeons)?

Something is really off here.

They have worked with USAID and FAO on HPAI. See: http://www.fao.org/docrep/017/ap388e/ap388e.pdf

.

**gsgs** · April 30, 2013, 09:05 PM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

while summer flu outbreaks were common centuries ago,
In a situation as in 2009 with normal seasonal winter flus in USA
and Europe for the previous 40 years
they would have probably noticed the unusual spread of ******
from America all around the world starting in ~May in NY
and yes, they would have considered it a pandemic, although a mild one.
Its quick spread around the world was obvious.

If there were some sort of barrier, that prevents consecutive pandemics
in less than x-years, then you would have to ask, what the reason
and the mechanism might be for that.
Immunity ? That doesn't even protect us so well from one year to
the next for the same strain.
And if the time was 11 years in the past then it might well
be 5 years now with air-travel.
-------------------------------------------

Hongkong had a H1-wave recently, which is going back now,
East China should be similar.
The next wave should be (>5?) months away

Cocirculation of Influenza Viruses - FluTrackers News and Information

http://www.flutrackers.com/forum/showthread.php?t=140223&page=2

China Influenza surveillance reports - FluTrackers News and Information

http://www.flutrackers.com/forum/showthread.php?t=150680

**Giuseppe** · May 1, 2013, 02:29 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

For the tropical flu season, we know there are two peaks: one during northern hemisphere winter and the second during spring/summer. Hardly flu disappears during the year in tropical zones.

H1pdm09 had some features that might be considered in the past as an intrasubtypic drift variants.

But a in depht genetical analysis demonstrated that it was not a fully human reassortant rathen than a human-swine-avian one.

Its ability to Exchange segments with other strains makes this virus unique and possibly a good parental strain for other future reassortants of animal origin.

The predominance of H1pdm09 in SE China this year may explain the skewed age-related H7N9 attack on the elderly people?

Has the innate heterotypic immune response been circumvented because of the antibody response toward old seasonal H1 strains in old people?

**gsgs** · May 1, 2013, 09:09 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

how would H1 explain the age pattern ?

And I'd liked an explanation that explains both,
the age and gender imbalance and why we don't see this with H5N1 !

new H1 segments also reassorted well in the H5 and H9
reassortment experiments

**Laidback Al** · May 1, 2013, 09:48 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

 Curiosity raises an interesting question about whether or not the 2009 pandemic would have been considered a pandemic without the genetic information about A(H1N1) pdm09. While we have made tremendous advances in the science of virus research, we have not yet developed a theoretical model that integrates this information with our more traditional understanding of the demographic/epidemiological dimensions of disease outbreaks and pandemics.
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**Pathfinder** · May 1, 2013, 10:22 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

1 May 2013 Last updated at 10:55 ET

H7N9 bird flu is a 'serious threat' - researchers warn

By James Gallagher
Health and science reporter, BBC News

...
There is concern over both the pace and severity of the outbreak.

There has been a relatively high number of known infections since the first case was detected in April.

Prof John McCauley, the director of a World Health Organization (WHO) collaborating centre in the UK, said: "It is unusual to get these numbers."
...
"The WHO considers this a serious threat," said Prof McCauley, "but we don't know at this stage whether this is going to spread from human to human."
...
The last major bird flu, H5N1, made the jump to people in 1997 and killed more than three hundred people -yet, it is still unable to spread between humans.

Predicting which viruses will become deadly on a global scale is impossible.
...
Often in pandemics older people have some immunity as they have lived longer and have been exposed to similar viruses before.

However, in this outbreak the ages of those infected ranges from two to 81.

Prof Farrar said: "That suggests there truly is no immunity across all ages, and that as humans we have not seen this virus before.
...
Prof Wendy Barclay, an influenza researcher at Imperial College London, said: "H7N9 might be one step closer to being able to become a pandemic than H5 is in nature at the moment."

It already has one of the five mutations when it is infecting birds.

Full text:

H7N9 bird flu is a 'serious threat' - researchers warn

http://www.bbc.co.uk/news/health-22364628

The outbreak of a new type of bird flu in China poses a "serious threat" but it is too soon to tell how far it will spread, flu experts have warned.

**Giuseppe** · May 1, 2013, 10:36 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

I don't think we have to wait until the H7N9 will have gained the putative mutations described in the article from BBC.

If health experts are growing a consensus opinion that this virus is poised to become pandemic, then the only thing to do is to increase pandemic alert level and proceed with vaccine manufacturing and preparedness acitivities without any further dealy.

**Giuseppe** · May 1, 2013, 11:18 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

Since this H7N9 seems to grow well in chicken's eggs, it is not much more simple to start monovalent vaccine production? Even with immunogenicity constraints, a moderately effective vaccines would be better than nothing.

**gsgs** · May 1, 2013, 11:26 AM

Re: Discussion - Chinese researchers speculate that Influenza A(H7N9) could cause a severe pandemic

vaccine is usually less efficient than a real infection.
And a vaccine doesn't replicate and spread by itself ...

And Indonesia can probably not afford a vaccine

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