Poultry, pigs and the next global pandemic

 (Published in ENRICH magazine 2021)

PIGS AND POULTRY could be the likely hosts of the next pandemic set to ravage the human race, perhaps over the next 40 years.

Lost in the tumult surrounding the global battle against the still uncontained COVID-19 coronavirus and its variants is the alarming news of outbreaks of a new strain of African swine flu (ASF) called "G4 EA H1N1," and avian influenza strains, specifically "H5N1.” These flu viruses carry the potential to be the next global pandemic but as of now represent a distant danger.

Medical experts worldwide have consistently warned the next pandemic is inevitable. Earlier this year, the World Health Organization (WHO), global epidemiologists and infectious hazard experts reiterated that warning, affirming the next pandemic is a statistical certainty.  In their professional opinions, a future pandemic is not a matter of "If," but of "When” and "How serious.”

The Center for Infectious Disease Research and Policy (CIDRAP) in Minnesota, whose aim is "to prevent illness and death from infectious diseases,” said there have been nine flu pandemics over the past 300 years. This statistic means one flu pandemic erupts every 30 to 35 years, or about three per century. CIDRAP estimates the 21st century might see up to five flu pandemics, however. 

The world has been hit by two pandemics so far this century. These are the 2009 H1N1 swine flu pandemic that also struck the Philippines and the raging COVID-19 pandemic, which isn’t caused by the flu virus but by the SARS-CoV-2 novel coronavirus.

In 2011, WHO said “the world is ill-prepared to respond to a severe influenza pandemic or to any similarly global, sustained and threatening public health emergency.” This prediction, made in the aftermath of the global 2009 H1N1 swine flu pandemic, was proven accurate with the onslaught of the ongoing COVID-19 pandemic starting December 2019.

Pandemic potential

G4 EA H1N1 swine flu has the potential, however low, to trigger a new pandemic if left unchecked. A peer-reviewed study conducted by Chinese researchers and published in the journal, Proceedings of the National Academy of Sciences (PNAS), in July 2020 issued the stark warning that further transmission of the G4 EA H1N1 swine flu strain found in Chinese pigs might see this virus “adapt and become a pandemic.”

Also known as the "G4 swine flu virus," swine-origin influenza A (H1N1) virus (S-OIV) is a virus strain discovered in China in 1996. It's a variant genotype 4 (or G4) Eurasian avian-like (EA) H1N1 virus that mostly affects pigs.

The H1N1 subtype has a long history as a killer of humans. It caused the horrific 1918 Spanish Flu pandemic estimated to have killed more than 50 million people worldwide and infected a third of the world’s population. It also caused the 2009 swine flu pandemic that claimed from eight to 27 lives in the Philippines.

The 2009 swine flu pandemic from January 2009 to August 2010 led to the deaths of more than 17,000 people worldwide, said WHO. This pandemic saw its first confirmed case in the Philippines in May 2009 and its first death in June.

Epidemiologists said some H1N1 strains are already endemic in humans. These endemic strains are responsible for a small fraction of all influenza-like illness, as well as all seasonal influenza. On the other hand, there are H1N1 strains endemic in pigs (swine influenza) and in birds (avian influenza).

The PNAS paper said "G4 EA H1N1 viruses possess all the essential hallmarks of being highly adapted to infect humans ... Controlling the prevailing G4 EA H1N1 viruses in pigs and close monitoring of swine working populations should be promptly implemented."

It noted the G4 viruses have the right characteristics for causing infections in people. These worrisome traits include the ability to grow well in human lung cells and to spread by respiratory droplets (much like COVID-19).

The study said the G4 virus "has shown a sharp increase since 2016, and is the predominant genotype in circulation in pigs detected across at least 10 provinces" in China. It documented three human cases of G4 infections in humans, all in China.

The study also found that some 10% of Chinese swine workers that had their blood samples taken had evidence of prior infections with G4 viruses. This suggests human infections are more common than previously thought.

Thankfully, the G4 virus can't be transmitted from person-to-person -- at least not yet. On the other hand, previous flu outbreaks have proven influenza viruses often jump from pigs to humans given time and favorable conditions.

 “The likelihood that this particular variant is going to cause a pandemic is low,” said Dr. Martha Nelson, who read the study. Dr. Nelson is an evolutionary biologist at the U.S. National Institutes of Health’s Fogarty International Center who studies pig influenza viruses and their spread to humans.

“You’re really not getting a good snapshot of what is dominant in pigs in China,” according to Dr. Nelson, who also said there is a need for more sampling.

Ominously, the study said G4’s inclusion of genes from the 2009 H1N1 pandemic “may promote the virus adaptation,” allowing for human-to-human transmission in the coming years.  It urged monitoring of farms and workers in China since further transmission might cause the G4 virus to “adapt and become a pandemic.”

The study said all the evidence indicates the G4 EA H1N1 virus "is a growing problem in pig farms, and the widespread circulation of G4 viruses in pigs inevitably increases their exposure to humans."  It said the G4 group of H1N1 swine influenza viruses have “the essential hallmarks of being highly adapted to infect humans” and are, therefore, of potential pandemic concern.

The study concluded G4 has been spreading in pigs in China since 2016, and has become the predominant genotype found in Chinese pigs today. The danger zoonotic transmissions might occur in the future led the study authors to urge closer monitoring of G4 EA H1N1 in China.

In the study, Chinese researchers analyzed 30,000 swabs collected from pigs at slaughterhouses in 10 Chinese provinces from 2011 to 2018. They found 179 swine influenza viruses, most of which were G4.

One consequence of the study was that in July 2020, the U.S. Centers for Disease Control and Prevention (CDC) began taking action to monitor and prepare the United States against this emerging public health threat from China. Among the actions taken by CDC were to ramp-up coordination with its public health partners in China, and requesting G4 virus samples from Chinese pigs.

CDC is also evaluating if an existing candidate vaccine virus against a closely related flu virus called “G5” can protect against the G4 viruses. If not, CDC will develop a new vaccine specific to G4 viruses.

H5N1 outbreak

In February 2020, China reported the latest outbreak of the H5N1 avian flu in the southern province of Hunan.  The Ministry of Agriculture and Rural Affairs confirmed an outbreak of a "highly pathogenic (or deadly) strain" of H5N1 bird flu at a farm in Shaoyang city in Hunan. It reported the culling 17,800 poultry following the outbreak at this and other farms.

This was the second H5N1 outbreak to hit China in 14 years. In 2006, an H5N1 outbreak struck eight countries, including China, leading to the deaths of 79 out of 115 positively diagnosed people worldwide, said WHO.

Highly pathogenic relates to the ability of a virus to kill chickens. It doesn't refer to how infectious a virus might be to humans, other mammals or other species of birds.

Health experts said most bird flu strains aren’t highly pathogenic and cause few signs of disease in infected wild birds. WHO said H5N1 is rare in humans but if H5N1 does infect humans, the mortality rate might reach a dreadful 60%. In contrast, the mortality rate for COVID-19 was estimated at 3.4% globally by WHO in March 2021 compared to 1% for seasonal flu.

H5N1 can be transmitted to humans typically through contact with dead birds or a contaminated environment. In July 2013, WHO said 630 confirmed human cases due to H5N1 infections from swine resulted in the deaths of 375 people since 2003 for a mortality rate of 60%,

"The virus does not infect humans easily, and spread from person to person appears to be unusual," said a statement from WHO. "There is no evidence that the disease can be spread to people through properly prepared and thoroughly cooked food."

Swine flu plus bird flu

Of great concern to the medical community it the mounting danger from a new bird flu pandemic triggered by shortages of pork. This danger is especially acute in China, which consumes more than half the world’s total pork production while producing more than a half of the global pig population. Pork is the most consumed type of meat in China.

Persistent pork meat shortages ignited a surge in imports while also spurring backyard poultry farming, a shift some health experts fear might trigger another bird flu pandemic..

“This is very scary because we know that there will be another pandemic,” said Dr. Kristina Osbjer, a veterinary epidemiologist, who used to work for the United Nations Food and Agriculture Organization (FAO). “Now, there is an increased risk of avian influenza being the origin.”

Global health authorities now see the relentless global spread of H5N1 influenza in birds as a significant and unprecedented pandemic threat.

"As long as avian influenza viruses circulate in poultry, sporadic infection of avian influenza in humans is not surprising, which is a vivid reminder that the threat of an influenza pandemic is persistent," said WHO about human infections from bird flu.

Other variants

Other avian flu strains with pandemic potential originating in birds are currently causing concern in China, South Korea and Japan.

In March 2021, Japan and South Korea reported their continuing struggle to control bird flu outbreaks that forced them to cull millions of chickens, ducks and quails. Japan is grappling against an outbreak of the highly pathogenic avian influenza H5N8 that began in in wild birds and poultry. Similar outbreaks have been reported in 12 other countries, mainly in Western Europe, since July 2020.

FAO said the outbreak in Japan and South Korea is one of two separate and ongoing bird flu epidemics. It said bird flu strains in Asia and one in Europe originated in wild birds spreading the disease during migration.

In December 2020, Japan culled more than 11,000 birds after a strain called H5N8 was discovered at an egg farm in Higashiomi, Shiga prefecture in the southwestern part of the country. The Ministry of Agriculture, Forestry and Fisheries declared the outbreak as Japan's worst of its kind.

"The virus found in Japan is genetically very close to the recent Korean viruses and, thus, related to viruses in Europe from early 2020 -- not those currently circulating in Europe," said Madhur Dhingra, a senior animal health officer at FAO. "This means that we currently have two distinct epidemics in eastern Asia and Europe.”

Also in December 2020, South Korea accelerated the culling of poultry in H5N8 affected areas. The Ministry of Agriculture, Food and Rural Affairs reported South Korea's first farm-related case in Jeongeup, some 290 kilometers south of Seoul, in late November. South Korea culled 5.8 million chickens, ducks and quails in the last two months of 2020.