By now, most of you have probably read news reports of a new flu virus that has been circulating in pig farms in China. Articles on the subject in popular media all use the phrase “pandemic potential.” None of the articles imply that a pandemic is imminent or that the virus is capable of human to human transmission.
But social media, amateur writers and fear, especially in this age of COVID-19, tend to distort information and leave us with the impression that a second pandemic is upon us. So, here is a summary of what the study is telling us. I do not have access to the paper, so most of the info here is culled from various reliable sources and the abstract of the paper.
Summary of the Findings
The authors of the study (peer-reviewed and published in the journal Proceedings of the National Academy of Sciences (PNAS)) analyzed nearly 30,000 swabs collected from pigs at slaughterhouses in 10 Chinese provinces collected between 2011 and 2018.
They found 179 different swine influenza viruses. A new strain called G4 or G4 reassortant EA H1N1 or G4 EA H1N1 seems to have become dominant since 2016, crowding out the earlier G1 variant.
The new virus strain is a blend of 3 influenza virus strains — the Eurasian avian-like (EA) H1N1 virus, the H1N1 strain that caused the 2009 pandemic (pdm/09), and a North American H1N1 that has genes from avian, human, and pig influenza viruses. (So, it is not a new virus but a new strain).
Experiments by the researchers show that —
- Similar to the 2009 pandemic pdm/09 virus, G4 viruses bind to human-type receptors (SAα2,6Gal)
- The virus proliferates rapidly in human airway epithelial cells, including cells from the trachea and lungs (in lab cell-culture tests).
- The virus is capable of aerosol transmission among ferrets, even ferrets in adjacent cages with no direct contact with each other
- Existing immunity to influenza virus does not provide protection against G4 viruses. The proteins on the surface of the virus are not similar to those of seasonal flu.
Further serological surveillance showed that the virus has infected humans in China —
- 10.4% (35/338) of swine workers tested positive for G4 EA H1N1
- For swine workers 18 y to 35 y old, 20.5% (9/44) tested positive
- 4.4% of a sample of non-workers were found to have antibodies
- However, the study mentions only two cases of swine workers treated for G4 flu. Does this imply that the virus produces only mild symptoms? Or that the population has some immunity to the virus?
- Also, the sample size seems low.
The prognosis
The good news first — human-to-human transmission has not been detected with this virus in spite of many years of prevalence. “The likelihood that this particular variant is going to cause a pandemic is low,” says Martha Nelson, an evolutionary biologist at the U.S. National Institutes of Health’s Fogarty International Center who studies pig influenza viruses in the United States and their spread to humans. But Nelson notes that no one knew about the pandemic H1N1 strain, which jumped from pigs to people, until the first human cases surfaced in 2009. www.sciencemag.org/...
The bad news — With such a large virus pool, in pigs and in humans, and with G4’s inclusion of genes from the 2009 H1N1 virus, there is a good probability that the virus can mutate and adapt to a form capable of aerosol transmission among humans. According to www.sciencemag.org/…, humans have no immunity to the avian influenza virus at the core of G4.
The good news again — this is what science is all about — detecting potential problems early and preparing for them. We know how to make vaccines for influenza viruses; we could easily make one for G4.
Expert Opinion
Experts have been quick to review the paper and explain its relevance and consequences. Here is a good thread on the topic by Dr. Angela Rasmussen, Virologist at Columbia University -
Another good thread from Prof. Bergstrom —
From Science Magazine -
The 2009 H1N1 Pandemic (H1N1pdm09 virus)
According to the CDC —
- The 2009 H1N1 swine flu killed between 157,000 and 575,000 people worldwide in its first year.
- Globally, 80% of (H1N1)pdm09 virus-related deaths were estimated to have occurred in people younger than 65 years of age. This differs greatly from typical seasonal influenza epidemics, during which about 70% to 90% of deaths are estimated to occur in people 65 years and older.
- Nearly one-third of people over 60 years old had antibodies against this virus, likely from exposure to an older H1N1 virus earlier in their lives.
- In the U.S., from April 12, 2009 to April 10, 2010, CDC estimated there were 60.8 million cases (range: 43.3-89.3 million), 274,304 hospitalizations (range: 195,086-402,719), and 12,469 deaths (range: 8868-18,306).
- The mortality rate was much lower than that of previous pandemics (1918 and 1968).
- The United States mounted a complex, multi-faceted and long-term response to the pandemic, summarized in The 2009 H1N1 Pandemic: Summary Highlights, April 2009-April 2010.
- A vaccine was quickly developed and the pandemic was declared over by the World Health Organization in August 2010.
Pig Population
Number of hogs and pigs in 2020 — from www.statista.com/...
- Worldwide - 677.6 million
- China - 310 million
- EU - 148 million
- USA - 78.6 million
The somewhat good news is that global pig stocks were 986.6 million in 2014 but dropped to 677.6 million in 2020, perhaps due to the 50% drop in China due to the African Swine Fever epidemic of 2019.
Pig Farming
For those who can stomach it, here is a video of pig farming in China. It is probably not much different in other countries.
How can we prevent a future pandemic?
The authors mention —
- Controlling the prevailing G4 EA H1N1 viruses in pigs and close monitoring in human populations, especially workers in the swine industry.
- Developing vaccines for pigs.
- Developing vaccines for humans.
Vaccines take time to develop, even for pigs. Vaccines for pigs for the African swine fever are still undergoing clinical trials.
In the long run, humankind may have to change course and eliminate animal farming, meat-eating and stick to eating plant based foods, including fake meats like the products from Impossible Foods, Beyond Meat and Omnipork. This idea has been advocated by many scientists and writers, for many reasons including the risk of disease and pandemics.
Epilogue
In summary, there is no imminent danger from the G4 EA H1N1 virus but vigilance and preparedness is warranted. In this age of global connectedness, viruses spread fast (tell us about it). We need more investment in public health and greater global cooperation among health organizations like the WHO and CDC. We need to improve our health care systems and make it affordable for everyone.
Also, COVID-19 and G4 EA H1N1 may be wake-up calls for how humanity is killing itself with animal farming practices and environmental destruction and may require us to accelerate the transition to a more sustainable and healthy plant-based future. Reducing factory animal farming will also help reduce greenhouse gases, water usage and pollution.
As Prof. Bergstrom aptly puts it -
or to put it more colorfully —
Further Reading
- Surge in diseases of animal origin necessitates new approach to health - report — www.fao.org/…
- Prevalent Eurasian avian-like H1N1 swine influenza virus with 2009 pandemic viral genes facilitating human infection — www.pnas.org/…
- Swine flu strain with human pandemic potential increasingly found in Chinese pigs — www.sciencemag.org/…
- Scientists Say New Strain of Swine Flu Virus Is Spreading to Humans in China — www.nytimes.com/…
- Flu virus with 'pandemic potential' found in China — www.bbc.com/…
- New Swine Flu Virus In China Has ‘Pandemic Potential,’ Here Are 7 Reasons Why — www.forbes.com/…
- G4 EA H1N1 — en.wikipedia.org/…
- 2009 H1N1 Pandemic (H1N1pdm09 virus) — www.cdc.gov/…