“One of the world’s most dangerous viruses in one of the world’s most dangerous areas,” WHO director-general says.
A little over three years ago, Chen Hualan – director of China’s National Avian Influenza Reference Laboratory – gave an interview to the Chinese News Agency Xinhua where she pegged the EA (Eurasian Avian-like) H1N1 swine virus (EAH1N1) as having perhaps the greatest pandemic potential of any of the novel viruses in circulation.
WASHINGTON, Dec. 28 (Xinhua) — The Eurasian avian-like H1N1 (EAH1N1) swine flu viruses, which have circulated in pigs since 1979, have obtained the ability to infect humans and may “pose the highest pandemic threat” among the flu viruses currently circulating in animals, Chinese researchers said Monday.
Her comments came after the publication of her paper (see PNAS: The Pandemic Potential Of Eurasian Avian-like H1N1 (EAH1N1) Swine Influenza) by Hualan et al. that described the Prevalence, genetics, and transmissibility in ferrets of Eurasian avian-like H1N1 swine influenza viruses.
In June of 2016, in Sci Rpts: Transmission & Pathogenicity Of Novel Swine Flu Reassortant Viruses we looked at a study where pigs were experimentally infected with one of these Eurasian-Avian H1N1 swine influenza viruses and the 2009 H1N1pdm virus.
Researchers generated 55 novel reassortant viruses spread across 17 genotypes, demonstrating not only how readily EAH1N1 SIV can reassort with human H1N1pdm in a swine host, but also finding:
`Most of reassortant viruses were more pathogenic and contagious than the parental EA viruses in mice and guinea pigs’.
A few months later, in EID Journal: Reassortant EAH1N1 Virus Infection In A Child – Hunan China, 2016, we reviewed the case report on a 30-month old child from Hunan Province, who was infected with one of these reassortant EAH1N1 – H1N1pdm viruses.
While we have our own, recurrent, swine-variant problem in North America (see The `Other’ Novel Flu Threat We’ll Be Watching This Summer), we are far from alone. Some recent swine-variant flu blogs from around the globe include:
While the article is still in press, and we don’t have a lot of information yet, the Journal of Infection is reporting on a new human infection with a novel reassortant of EA-H1N1 and H3N2 in China.
Jing Lua,b,1,Lina Yia,b,, Yi Jingc, Hanqing Tand, Wei Maid, Yingchao Songa, Lirong Zoua, Lijun Lianga,Hong Xiaoa, Min Kanga, Jie Wua, Tie Songa, Changwen Kea,
- Retrospective surveillance on ILI samples identifies a S-OIV H3N2 (A/GD/277/H3N2/2017) which caused a spill-over infection in a young child.
- Hemagglutination-inhibition test shows A/GD/277/H3N2/2017 is antigenically distinct from seasonal H3N2 viruses currently circulating in the human population.
- A/GD/277/H3N2/2017 is a novel reassortant of EA-H1N1 and H3N2 previously circulating in swine in Southern China.
- Phylogenetic analysis shows A/GD/277/H3N2/2017-like virus caused another spill-over infection in Vietnam in 2010 suggesting the firm establishment of this swine lineage in Southeast Asia.
A reminder that, while we watch avian flu for signs of mammalian adaptation, there are billions of (wild and domesticated) pigs in the world that already carry mammalian-adapted flu viruses.
Testing and surveillance is seriously lacking, but the emergence of novel swine viruses remains a global concern, with new strains continuing to pop up in North America, South America, Europe and Asia.
Their ability to reinvent themselves through reassortment with human, avian, and swine viruses, the shipment of live pigs nationally and internationally, and the growth in the global pork industry in general, pretty much ensures this threat is only likely to increase over time.
Although past performance is no guarantee of future results, with our county and state fair season beginning in June, it would not be unexpected to see outbreaks – in swine, and humans – in the coming months.
|Swine Variant Human Cases : 2010-2018 – Credit CDC|
For now, swine variant flu infection remains a relatively minor public health threat in the United States, with most infections producing only mild or moderate illness. But flu viruses are constantly changing, and so the CDC’s Risk Assessment on H3N2v and other swine variant viruses reads:
Sporadic infections and even localized outbreaks among people with variant influenza viruses may occur. All influenza viruses have the capacity to change and it’s possible that variant viruses may change such that they infect people easily and spread easily from person-to-person. The Centers for Disease Control and Prevention (CDC) continues to monitor closely for variant influenza virus infections and will report cases of H3N2v and other variant influenza viruses weekly in FluView and on the case count tables on this website
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