Post Reply - A new pandemic

see graphic above

   https://afludiary.blogspot.com/2025/04/emerg-microbes-inf-eurasian-1c-swine.html or https://afludiary.blogspot.com/2025/04/emerg-microbes-inf-eurasian-1c-swine.html ;
In late April sixteen years ago - at at time when H5N1 was our biggest pandemic concern - the world was blindsided by a swine-origin H1N1 pandemic that began in Mexico, and quickly swept the globe. 
While milder than the three influenza pandemics that preceded it (1968, 1957, 1918), the CDC had this to say about its impact on a younger cohort in 2012's First Global Estimates of 2009 H1N1 Pandemic Mortality Released by CDC-Led Collaboration.
2009 H1N1 Pandemic Hits the Young Especially Hard

This study estimated that 80% of 2009 H1N1 deaths were in people younger than 65 years of age which differs from typical seasonal influenza epidemics during which 80-90% of deaths are estimated to occur in people 65 years of age and older.
Although the pandemic lasted barely a  year, it reinforced our concerns over the ability of swine-origin H1, H2, or H3 viruses to spillover into humans (see graphic above).  Since then we've seen more than 500 such spillovers in the United States alone. 
We've seen similar reports from Europe, South America and Asia, although surveillance of pigs and humans for swine flu (even in the United States and Europe) is extremely limited. 
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The ECDC maintains a Swine influenza Factsheet, which describes the introduction and spread of influenza viruses in European pigs.
Current influenza viruses in European pigs
Avian-like swine A(H1N1) influenza viruses (SIVs) of the subtypes A(H1N1), A(H3N2) and A(H1N2) are enzootic and widespread in swine producing regions of Western Europe. The first known introduction of human influenza virus into swine populations occurred after the Spanish flu in 1918 and this lineage was called ‘classical swine’ H1N1 (or lineage 1A). This lineage is still present in pigs in the Americas and Asia, but has not been detected in European pigs in the last two decades.

The first significant outbreak of an avian A(H1N1) influenza virus lineage occurred in 1979 and led to the establishment of an ‘avian-like’ A(H1N1) virus lineage in European pigs. This virus, referred to as Eurasian avian-like 1C lineage, rapidly established itself in Europe and has continued to circulate in swine until the present day.

Contemporary swine A(H3N2) influenza viruses in European pigs descend from early human influenza A(H3N2) pandemic strains, and have diverged substantially genetically and antigenically from contemporary human viruses. The A(H1N2) influenza viruses were established in Europe with the reassortment of swine A(H3N2) viruses and a human-seasonal A(H1N1) virus (H1huN2) and to date are still circulating among European pig populations.
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Essentially, while there are some crossovers, the reservoir of swine viruses differs around the world - and with the ability of influenza viruses to reassort - they continue  to evolve and diversify.  In addition to the 3 North American swine-variant viruses on the CDC's IRAT list, we continue to watch the evolution of China's EA H1N1 `G4' virus,  Brazil's H1N2v virus, and occasional spillovers of H1N1 in Europe. 
But the reality is, most of the world isn't even looking.  We could easily be blindsided again. 
All of which brings us to a cautionary research article, published yesterday in the journal Emerging Microbes & Infections, which find that the Eurasian 1C swine influenza virus (described above) has significant pandemic potential. 
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In Fall of 2021, multiple human cases of an H1N2 variant from clade 1C.2.4 were observed, including one in France. This was the first human detection of 1C.2.4 in France and represents an evolutionary expansion of 1C in the swine population. In this study, we utilize a decision tree (12) (Figure S1) to determine the pandemic potential of A/Bretagne/24241/2021, a 1C.2.4 variant virus (referred to herein as 1C H1N2v) through examination of viral phenotypic traits as well as interspecies and intraspecies transmission.
         (SNIP)

Conclusions

The endemic nature of swine H1 1C strains in the pig population in Europe and Asia and sporadic zoonotic events suggest a leaky barrier at the animal-human interface. Low levels of immunity against the virus in US and Asian populations and efficient inter- and intra-species transmission suggests a pandemic threat of 1C H1N2 viruses.
 Although prior immunity with H1N1pdm09 decreased disease severity it did not disrupt transmission of 1C H1N2v virus in ferrets, suggesting that H1 immunity in humans will not block airborne transmission. Taken together, risk assessment of 1C H1N2v virus would indicate that it is in the higher pandemic risk category and should be continued to be monitored for spillover into humans.
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While another H1Nx pandemic might not prove as severe as one from H5N1, we can't assume that it would be mild for everyone. After all, prior to SARS-CoV, MERS, and COVID all coronaviruses were considered `mild' and incapable of producing a pandemic.   

As any epidemiologist will tell you . . . If you've seen one pandemic, you've seen one pandemic. 
Swine H1, H2, and H3 viruses presumably have an easier time crossing the species barrier, and infecting humans, since they are already pre-adapted to a mammalian host.  And as we've discussed previously, all human pandemics going back to the late 1800s have stemmed from H1, H2, or H3 subtypes. 
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Although the public health risks are considered low, the CDC advises those who are at higher risk of serious flu complications (including children under 5, adults over 65, pregnant women, and those with certain chronic medical conditions), to avoid pigs and the swine barn altogether.

DJ, STOP eating pigs ! Decrease the number of farm animals to decrease pandemic risks !!!! Competition on prices of meat means the farms doing worse on disease prevention may "win"...but at the end YOU pay !!!!

And again-human immunity was able to limit flu risks...
-Aging is decreasing immunity protection...
-CoViD, Measles decrease human protection
-Anti-vax stupidity decreasing human protection...

The higher the level of immunity in humans the less chances for diseases...From an epidemiology point of view if only 25% of the population has immunity it may not even slow down a disease...

And CoViD does NOT exclude flu, flu not exclude CoViD...it increases the risks for all kinds of co-infections !