The Flu Saga: H1N1, the next pandemic? (Part 1)

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Health experts are already thinking of the next potential pandemic while the world is currently waging war against the novel coronavirus.

This is no longer surprising, as the world’s relative unpreparedness for the SARS-CoV-2 contagion dealt it a heavy blow proving that the flu threat remains very real.

A research article published in Proceedings of the National Academy of Sciences by Honglei Sun and co-authors reported that the ongoing surveillance on influenza since 2011 got them to identify a recently emerged genotype 4 (G4) re-assortment Eurasian avian-like (EA) H1N1 virus, which bears resemblance to the H1N1 virus that caused the 2009 Swine flu pandemic and killed about 285,000 people.

Pigs are the intermediate hosts for the generation of pandemic influenza viruses.

This is the reason why systematic surveillance of influenza viruses in pigs is a key measure for warning against the emergence of a potentially pandemic causing influenza.

"This colorized negative stained transmission electron micrograph (TEM) depicted some of the ultrastructural morphology of the A/CA/4/09 swine flu virus." by C. S. Goldsmith and A. Balish, CDC is in the Public Domain, CC0
“This colorized negative stained transmission electron micrograph (TEM) depicted some of the ultrastructural morphology of the A/CA/4/09 swine flu virus.” by C. S. Goldsmith and A. Balish, CDC is in the Public Domain, CC0

The new strain, known as G4 EA H1N1 (further shortened as G4) has been common in China’s pig farms since 2016 and according to the study, replicates efficiently in human airways.

The study also showed that it can be efficiently transmitted among ferrets, an animal used to study flu viruses.

These features led the research team to declare that it “possesses all of the essential hallmarks of a candidate pandemic virus” and poses “a serious threat to human health.”

Further adaptation and mutation of the virus raises concerns for the possible generation of a new contagion that could cause a pandemic.

So far, it has infected a number of people without causing disease; 10 percent of 338 people tested who worked with pigs had antibodies, or immune proteins that recognize the virus — a sign that they had recovered from a previous infection.

Antibodies can stick around for years after an infection, so it is not known when the workers were exposed to the virus.

It’s also unclear whether those people had symptoms while they were infected. It’s possible that the virus doesn’t cause severe disease, so the infections went unnoticed. If the workers did have symptoms, there’s also a chance that the signs of illness were indistinguishable from regular flu. There is a slight possibility that the test picked up immune proteins that recognize another flu virus, not G4.

How pigs get the flu

The CDC reports four types of Influenza viruses. Most of the seasonal flu we experience comes from Type B influenza while type A influenza are usually harbored in animals, most especially birds – and they do not readily infect humans as much as type B influenza.

Since we are not usually hosts to type A Influenza viruses, we don’t have that much immunity to them. So when a type A virus suddenly acquired an adaptation or mutation that helps it spread to humans, this is where it becomes a threat.

Spanish flu was an Influenza virus (influenza A subtype H1N1). They are denoted by their antigenic type either A, B, C or D. Influenza A is the deadliest of the 4, and is responsible for most of the flu outbreaks. The subtype names come from H and N antigens – numbered as they are discovered (H1N1, H2N2, H3N2, H5N1 etc) the swine flu pandemic of 2009 was a novel H1N1 strain and bird flu (H5N1) continues to have multiple outbreaks annually in various places worldwide. (Read more on our story on the history of pandemics).

Influenza viruses bind to a protein called sialic acid to break into cells. Birds and people have different types of this protein in their upper airway, but pigs have both. That makes pigs not only susceptible to swine-specific flu strains but also to flu viruses from birds and humans. As a result, the animals often become influenza mixing pots. Once in pigs, bird, swine and human flu viruses can exchange genetic material — called reassortment — giving rise to new strains.

The World Health Organization coordinates a Global Influenza Surveillance and Response System, which gathers data from member countries to monitor seasonal and pandemic flu. Right now, only pigs in China are known to carry the G4 flu strain.

There is no evidence that G4 or similar viruses are in other countries.

“It’s not an immediate threat where you’re seeing infections,” Anthony Fauci, director of the U.S. National Institute of Allergy and Infectious Diseases in Bethesda, Md., said in a U.S. Senate hearing on June 30. “But it’s something we need to keep our eye on, just the way we did in 2009 with the emergence of the swine flu.”

The Pandemic we’re preparing for

In one of WHO’s spotlight articles, they reported on a story about 100 passengers in a flight from Dubai to New York in September 2018, who fell ill with respiratory symptoms. Health officials were concerned that they might be carrying a serious respiratory illness called MERS-CoV (Middle East respiratory syndrome coronavirus) and quarantined the plane until further health checks could be completed.

Testing showed that several were positive for the influenza virus, which can be easily spread when people are in close contact or in contained spaces such as airports and planes for several hours.

Influenza may not always be thought of by most people as a serious illness — the symptoms of headaches, runny nose, cough and muscle pain can make people confuse it with a heavy cold.

Yet seasonal influenza kills up to 650,000 people every year. That is why influenza vaccinations are so important, especially to protect young children, older people, pregnant women, or people who have vulnerable immune systems.

What most of us think of as ‘the flu’ is seasonal influenza, so-called because it comes around in the coldest season twice a year in temperate zones of the world, and circulates year-round in the tropics and subtropics.

The influenza virus is constantly mutating, essentially putting on ever-changing disguises, to evade our immune systems. When a new virus emerges that can easily infect people and be spread between people, and to which most people have no immunity, it can turn into an outbreak and subsequently a pandemic.

100 years after the Spanish Flu pandemic, the world continues to be ever vigilant of Influenza. Health authorities like the World Health Organization has various “Pandemic Preparedness” Guidelines, Surveillances and Response systems drawn out in case a new strain of influenza wreaks havoc globally.

Influenza is the pandemic we were preparing for, but we hope it will not come to meet it.

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