#15,800
Although the last thing anyone wants to think about right now is the rise of another pandemic - either during, or in the immediate aftermath of COVID - there are legitimate reasons to be concerned. Nature's laboratory remains open 24/7, and the number of zoonotic viruses with pandemic potential continues to climb.
Less than a week ago, in CDC Selects New Swine-Variant EA H1N1 Virus For The Top Of Their IRAT List, we looked at the latest addition to the CDC's IRAT (Influenza Risk Assessment Tool) list of zoonotic flu viruses with pandemic potential.
On the influenza front alone, over the past decade we've seen the rise of H5N6, H5N8, H7N9, and the EA H1N1 `G4' (and other) variant flu viruses. While COVID 19 won the pandemic sweepstakes in 2020, there are plenty of other coronaviruses - including MERS-CoV - with pandemic potential in the wild.
And of course, there is always Clade X, the virus that isn't on our radar yet, that may be quietly spreading, and evolving, towards becoming a pandemic threat.
Less exotic, but still capable of hitting us very hard, are seasonal flu viruses (H1N1 & H3N2) that have been kept at bay for nearly a year since the emergence of COVID, primarily due to social distancing and universal masking.
With each passing month, our collective immunity to these seasonal threats wanes a little more. Meanwhile, without the competition from the dominant seasonal flu strains, we could see new, antigenically distinct, variants emerge.
There are a plethora of other respiratory viruses, including adenoviruses, enteroviruses, RSV, and others that are similarly suppressed right now. How they may fare when the masks eventually come off, and we begin intermingling again, is unknowable.
Like it or not, we are engaged in an unplanned global field experiment, where our fight against one viral threat (COVID) could have unexpected impacts on other threats that may emerge in the months and years ahead.
Ten years ago today (Feb 12th, 2011), in The Third Epidemiological Transition, I wrote about the work of the late (May 22, 1936 - May 15, 2014) anthropologist and researcher George Armelagos of Emory University, who posited that since the mid-1970s the world has entered into an age of newly emerging infectious diseases, re-emerging diseases and a rise in antimicrobial resistant pathogens.
Since then we've seen a veritable rollercoaster of infectious disease threats emerge, and there are few reasons to expect that will change any time soon. We neglect pandemic preparedness for the next one at our own peril.
All of which brings us to a recent dispatch, published in the CDC's EID Journal, on a 2019 zoonotic infection of a Dutch farmer with a Eurasian Avian-like Swine H1N1 virus. Swine variant viruses are a particular pandemic concern because they are thought to have less far to evolve to spread in humans (see Are Influenza Pandemic Viruses Members Of An Exclusive Club?).
While only rarely reported, these types of infections almost certainly happen with far greater frequency than we know, and each one is another opportunity for a swine-origin virus to better adapt to humans.
First a link and some excerpts from the report (follow the link to read it in its entirety), then I'll return with a bit more.
Volume 27, Number 3—March 2021
Dispatch
Human Infection with Eurasian Avian-Like Swine Influenza A(H1N1) Virus, the Netherlands, September 2019
Anna Parys, Elien Vandoorn, Jacqueline King, Annika Graaf, Anne Pohlmann, Martin Beer, Timm Harder, and Kristien Van Reeth
Author affiliations: Ghent University, Merelbeke, Belgium (A. Parys, E. Vandoorn, K. Van Reeth); Friedrich-Loeffler-Institut, Greifswald Insel-Riems, Germany (J. King, A. Graaf, A. Pohlmann, M. Beer, T. Harder)
Abstract
We report a zoonotic infection of a pig farmer in the Netherlands with a Eurasian avian-like swine influenza A(H1N1) virus that was also detected in the farmed pigs. Both viruses were antigenically and genetically characterized. Continued surveillance of swine influenza A viruses is needed because of human infection risk.
Eurasian avian-like swine influenza A(H1N1) viruses (IAVs) are entirely derived from a precursor virus of avian origin (1) and have been enzootic in the swine population in Europe since 1979 and in Asia since 1993. Zoonotic infections with such viruses, which are then termed H1N1 variant (H1N1v) viruses, occur sporadically. Most cases occur in humans who have direct exposure to pigs. Since 1986, several human cases of Eurasian avian-like H1N1 swine IAV have been reported in Europe (2–4) and China (3,5).
These events reflect the possibility of Eurasian avian-like H1N1 swine IAV transmission from swine to humans. In this study, we report an infection with a Eurasian avian-like H1N1 swine IAV in a pig farmer and his pigs in a herd in the Netherlands. We also conducted whole-genome characterization of viruses from the man and the pigs.
The Study
On September 18, 2019, acute respiratory disease was observed in a 43-year-old man (farmer) and his 14-week-old fattening pigs and gilts. The pigs of this closed farm showed coughing, anorexia, tachypnea, dyspnea, and lethargy. Two days earlier, a 44-year-old man (animal caretaker) had reported similar symptoms. The sows of this herd (n = 420) were vaccinated against swine IAVs with Respiporc FLU3 vaccine (Ceva, https://www.ceva.com), but the farmer and animal caretaker were not recently vaccinated against human seasonal influenza viruses. Both humans and the pigs recovered completely within 10 days after the first appearance of signs or symptoms. Family members and close contacts of the men did not show development of influenza-like symptoms.
Six days after onset of disease, nasal swab samples were collected from the farmer, the animal caretaker, and 6 symptomatic pigs. Human samples were collected by self-sampling, and informed consent was obtained from the farmer and the animal caretaker. Subsequently, samples were shipped to the Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University (Merelbeke, Belgium).
Upon inoculation into MDCK cells, influenza A virus was isolated from the sample of the farmer and from a pooled sample of the pigs; no virus was isolated from the animal caretaker. Public health authorities in the Netherlands were notified about the H1N1v infection. The human H1N1v isolate was named A/Netherlands/Gent-193/2019, and the swine H1N1 isolate was named A/swine/Netherlands/Gent-193/2019.
Virus neutralization tests with swine antiserum against swine IAVs of the H1N1, H1N2, and H3N2 subtypes showed an antigenic relationship between both newly discovered isolates and Eurasian avian-like H1N1 swine IAVs from 1998 and 2010, as well as the prototype influenza A(H1N1)pdm09 (pH1N1) A/California/04/2009 virus. Serologic cross-reactivity with H1N2 or H3N2 swine IAVs was not observed (Table 1).
(SNIP)
Conclusions
We report another zoonotic infection with a Eurasian avian-like H1N1 swine IAV in Europe since the emergence of the virus in 1979 (2–4). No further human-to-human transmission was reported, although it cannot be excluded that the farmer was infected by the animal caretaker. The nasal swab sample from the caretaker might have tested negative because it was collected as late as 8 days after he reported influenza-like symptoms.
The swine antiserum against the pH1N1 virus cross-reacted with the swine H1N1 isolate from this investigation (Table 1) but had a 192-fold lower virus neutralization titer against the human H1N1v isolate. Therefore, it is unlikely that current human seasonal vaccines would provide cross-protection against the human H1N1v isolate. This finding is consistent with our recent investigations of human serum samples for antibodies against 8 H1 swine IAVs representing 7 predominant H1 clades of swine IAVs; only 55 (10%) of 549 human serum samples had hemagglutination inhibition titers >40 against a European avian-like H1N1 swine IAV of clade 1C.2.1, which is predominant in swine in Europe (11), compared with 24%–54% against 5 other clades (12). These data point toward a relatively greater zoonotic risk for avian-like H1N1 swine IAVs from Europe and are consistent with previous studies about Eurasian avian-like H1N1 swine IAVs from China (5,13). Our data further support the notion that Eurasian avian-like H1N1 swine IAVs need to be monitored closely.
We found several amino acid substitutions between the H1N1 swine isolate and the H1N1v human isolate, but their role remains obscure. The past 2 decades have seen an unprecedented increase of data for putative mammalian-adaptive mutations of avian influenza viruses. The known genetic markers are mainly based on studies with wholly avian viruses of various HA subtypes in mammalian cell culture or in ferrets. Knowledge of amino acid substitutions that might enable adaptation of swine-adapted influenza viruses to humans, in contrast, is almost nonexistent (14). This finding is true for Eurasian avian-like H1N1 swine IAVs, as well as for the pH1N1 virus, which is the only known swine-origin virus with the ability to spread efficiently between humans. Our study highlights the need for experimental research on this topic and for continued surveillance of swine IAVs because of the risk for human infection or zoonotic spread.
Ms. Parys is a PhD student in the Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium. Her primary research interests are the pig as a model for development of broadly protective influenza A vaccines and public health implications of swine influenza.
(Continue . . . .)
The CDC's Responds to the PNAS EA H1N1 `G4' Swine Flu Study
ECDC Risk Assessment: Eurasian avian-like A(H1N1) swine influenza viruses
WHO Novel Flu Summary & Risk Assessment - July 2020
FAO/OIE/WHO Tripartite Statement on the Pandemic Risk of Swine Influenza
H1N2 variant [A/California/62/2018] Jul 2019 5.8 5.7 ModerateH3N2 variant [A/Ohio/13/2017] Jul 2019 6.6 5.8 Moderate
H3N2 variant [A/Indiana/08/2011] Dec 2012 6.0 4.5 Moderate
We continue to watch other swine variant viruses of concern around the globe (see list below), but for the vast majority of the world, little or no surveillance is underway. All of which leaves us incredibly vulnerable to being blindsided again.
For more on swine variant viruses, you may wish to revisit:
