# 4349
Influenza A today appears to be at a crossroads, with the H1N1v (variant) virus largely in retreat and no signs (yet) of a resurgence of the seasonal strains we’ve been saddled with for the past three decades.
And that begs the question – what happens next?
I will confess at the outset, I don’t know the answer to this question, and so I’ll be making no predictions. But that doesn’t mean we can’t discuss some of the possibilities.
And there are, quite frankly, a lot of possibilities . . .
The most likely scenario right now seems to be that the novel H1N1 virus will settle in over the coming months as our dominant seasonal flu strain and remain so until something `more fit’ - to which mankind is susceptible - comes along to knock it off its perch.
But likely scenarios are perilous things.
If you had asked a year ago what the next twelve months would bring, few scientists would have dared suggest that a `weak sister’ H1N1 virus would leap forth from pigs to humans in (of all places) North America, sweep across the world in record time as a high morbidity-low mortality pandemic, and drive out the other seasonal strains along the way.
Even if this `most likely scenario’ holds true, there are a lot of avenues it could follow. To simply say it becomes a `seasonal flu’ is to leave out a lot of detail.
Will its virulence change, or will it begin to impact the elderly population more over time?
Professor Ian York who pens the Mystery Rays blog commented on here yesterday that between vaccinations and acquired immunity `nearly 3/4 of children, and over half of adults, should now be immune to the swine-origin H1N1’ (US numbers) which is a pretty good step towards `herd immunity’.
Enough so that it casts doubt on whether we will see a major resurgence of the virus this spring in North America.
Once we get good seroprevalence studies of the general population, we’ll have an even better idea of our level of immunity in the wake of this pandemic.
Unknown right now is the incidence of asymptomatically acquired immunity.
Which raises interesting questions for next fall as well.
As we as a society grow closer to acquiring `herd immunity’ the virus must either mutate or `drift’ antigenically to evade that immunity, or it will eventually run out of hosts and die.
My good friend Scott McPherson gives us a great run down of this scenario, along with the concerns of Professor John Oxford, in his latest screed entitled Parsing the numbers on the latest CDC H1N1 swine flu report.
A mutation or drift in the H1N1v virus seems likely, but the question is . . . how long with that take?
Will it happen during the Southern Hemisphere’s upcoming flu season? Or will the virus lay low next year, like it did in the year following the 1957 pandemic, only to rise again a year or two later?
We’ve less than 100 years of scientific observation of flu viruses to draw upon, and as H5N1 and H1N1v have shown, the `rules’ we thought we understood about influenza are subject to change.
If H1N1v fails to mount an aggressive return in the fall of 2010, will that leave the door open to other viruses to take its place?
Influenza, even in a normal year, represents less than 20% of all flu-like illnesses.
Coronaviruses, metapneumovirus, parainfluenzavirus, respiratory syncytial virus (RSV), any of the myriad Rhinoviruses (Common cold), and some adenoviruses can all cause ILI’s, or influenza-like illnesses.
Even last October – near the height of the pandemic wave in the United States – (see ILI’s Aren’t Always The Flu) more than 70% of the samples submitted to the CDC proved to be something other than influenza A.
In the absence of H1N1v, could 2010 become a big B influenza year? Or a year where RSV or an adenovirus is the major player?
If you take influenza A out of the equation, does that give some other virus a competitive advantage?
The dynamic between these viruses isn’t well understood, just as it isn’t clear how a novel strain like H1N1v managed to pretty much take out seasonal H3N2, even though there remains a susceptible population to it.
Does a waning H1N1v leave the door open for a return of the the H1 and H3 seasonal viruses? And if not, in the absence of other influenza A viruses, does this convey to H5N1 or any of the H7 or H9 avian influenza viruses any sort of evolutionary advantage?
I don’t think anyone really knows.
But it is going to be fascinating to watch.
And just as the rules of influenza appear to be malleable and subject to change, so too is Flublogia – that little Internet world comprised of flu forums, newshounds, and flu blogs that sprang up roughly five years ago in response to the SARS and bird flu threats.
Crof, Scott, and I have all strayed from flu-centric topics in the past, and with a variety of emerging infectious diseases out there deserving of our attention, I expect you’ll see a good deal more of that in the future.
The Reveres at Effect Measure, Vince Racaniello at Virology Blog, Maryn McKenna of Superbug Blog, and Ian York at Mystery Rays have always been eclectic health/science bloggers, and the flu forums like Flu Wiki and FluTrackers (among others) have watched other disease threats for years.
While I can’t predict with any confidence what direction influenza will take over the next year or two, I am confident that we will have no lack of important health and science topics to write about in the months and years to come.
MRSA, Malaria, C. Dif, Dengue, Chikungunya, Ebola, TB, HIV/AIDS, Cholera, Hendra, Nipah, Small Pox, Bubonic Plague, Lassa Fever, Marburg, SARS, RSV, along with dozens more . . . and yes, even Pathogen X – the one we’ve yet to identify – are all worth our notice.
Along with influenza, of course.
Rest assured, that with or without a pandemic.
Flublogia marches on.
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A brief personal note:
As today’s blog illustrates, much of what I write about is inspired by what I read and learn from other sources. No blogger is an island, and that is particularly true in Flublogia.
While I’ve been pondering the issues I wrote about today for some time, they only solidified into a blog post after reading Ian York’s comments yesterday, Scott’s blog last night, several recent entries from Crof, and having had conversations with several others in Flublogia in recent days.
A more collegial group you’d be hard pressed to find, and I owe them a large debt of thanks. You’ll find I name names in Reliable Sources in FluBlogia, so I’ll spare you a detailed list today.
Collectively they’ve proved that difficult subjects like pandemics, emerging infectious diseases, and natural disasters can be discussed reasonably, scientifically, and without shrill overtones or alarmism.
And that is something we need more of on the Internet.
