Why might the swine flu virus in humans spread again?


London- (BBC):

Imagine that you listen to the BBC and the broadcaster announces in his British accent that the number of deaths from the disease, according to the World Health Organization, exceeded 700 cases within a week, bringing the death toll in the world to 5,700. In Europe, Ukraine closed schools and cinemas and banned public gatherings. In Britain, the number of injuries doubles every week. In the United States, the US President declared a state of national emergency.

This news may sound familiar today, but these events occurred in 2009, when the last global flu pandemic, known as swine flu or “H1N1”, broke out.

Scientists believe that the “H1N1” virus began its journey from pigs in a small region of central Mexico in January 2009. By March, the first cases of the virus were detected in California and Texas. In June, the virus spread to 74 countries around the world. The following year, the World Health Organization declared the end of the pandemic, which had killed between 151,700 and 575,400 people, according to a study published in the Lancet Infectious Diseases journal.

The global efforts to distribute the swine flu vaccine, led by the United States, contributed to containing the epidemic, but the “H1N1” virus still exists, and it spreads annually in the form of seasonal flu epidemics and causes moderate symptoms, severe complications and may lead to death.

Scientists around the world are watching H1N1 flu and other types of swine flu to learn how these diseases originate and develop ways to contain future viruses before they turn into a pandemic. This task has become difficult given human activities, from methods of food production to patterns of travel and transportation.

To this end, a large-scale global program was launched at 2,500 European pig farms, and scientists collected samples from more than 18,000 pigs. And they discovered cases of influenza A viruses – which may be transmitted between humans and cause epidemics – in more than half of the farms from which samples were collected, especially in high-production areas such as Denmark, the French region of Brittany, northwest Germany and the Netherlands.

In other words, they discovered a pandemic that was waiting for an opportunity to spread.

Risk factors

In 1910, the German scientist Friedrich Löffler, the world’s oldest virus research institution, was founded on the island of Reims, on the northeastern tip of Germany. While it is now possible to establish virus research institutes anywhere, thanks to biosecurity measures, Loeffler chose this island as the headquarters for his virus research, after many diseases leaked from his laboratory to the residents of the area. The Friedrich Löfler Institute is now Germany’s largest center for zoonotic diseases.

The center includes laboratories and facilities for animal experimentation and barns for raising pigs, chickens, cattle and wild boars. An area has been designated to monitor bird flu patterns and new virus strains, by attracting wild birds that cross the area during their migration.

Martin Behr, head of the Friedrich Löffler Institute’s Diagnostic Virology Institute, leads the team on pig specimen collection in Europe. The team found four communicable influenza viruses that could potentially cause a pandemic. Meaning that it may infect humans, and it has the ability to spread among humans, and there is no vaccine or innate immunity against it.

Although the viruses that have been found so far, none of them possess all the properties necessary to spread between humans and turn into a pandemic, if they manage to adapt, the risks of a new pandemic will rise. The team also noted that the prevalence of these viruses among pigs is increasing.

“We were surprised that 30 percent of the pigs were infected with influenza A virus, and this percentage is not small,” Bear says. Like humans, pigs are more susceptible to infection with viruses because their bodies have not developed the antibodies needed to fight them. Pigs are slaughtered in Europe, where production is intensive, before the age of six months, which is why many pigs in Europe are susceptible to infection with viruses.

It is true that Europe has some advantages that make it less vulnerable to the spread of diseases compared to other regions of the world, as it is a rich continent and many countries have good health care systems, and it has some of the best scientists in the world and its relatively moderate weather, but we have now realized that all these factors do not make it. Spared from the epidemic.

In parallel with the increase in the population, the demand for protein sources has increased. And pork production in Europe accelerated to meet the unprecedented demand. But this pace of production leads to the emergence of new diseases.

Tim Harder, head of the Animal Influenza Reference Laboratory at the Friedrich Fuller Institute, says there is a correlation between the frequency of protein production in Europe and the viruses that have emerged recently.

Harder says, “In 1995, the largest pig farms had 200 pigs, but now there are farms with between 2,000 and 20,000 pigs. This significant increase in the size of farms may change the patterns of influenza virus outbreaks.”

Twenty years ago, the emergence of a new virus on a small farm was not a threat, because it quickly disappeared without infecting many animals. But now, hundreds of pigs are born on large farms every day, and once the influenza virus appears it may quickly spread and remain. It may appear in certain seasons year after year, or it may affect animals throughout the year.

“Pig farms have become (thanks to extensive pig breeding), a breeding ground for viruses,” says Hard.

Animal warehouses

Fortunately, the symptoms of the “H1N1” virus, if you are in good health, are usually mild and may recover within two weeks. But the problem is that influenza viruses cross barriers between species and mix with other influenza strains within the host’s body, and lead to the emergence of new viruses that may be able to cause severe diseases, deaths and global repercussions, as is the case with Covid-19 disease.

Pigs have been shown to be an ideal reservoir for these different strains of viruses to mix.

“Pigs play the role of a test tube in which influenza viruses that are transmitted to pigs from humans and possibly birds and other species mix together, and this mixing creates new genetically modified strains that are more deadly than The original species may pass back from pigs to other species. “

Lewis attributes the presence of many strains of influenza in European pigs to the fact that pigs become infected with seasonal influenza from humans annually. That is why pig farmers are advised to get the flu vaccine annually. But this problem is not unique to Europe, but viruses are transmitted between humans and pigs in various parts of the world.

Pigs are not only infected with viruses from humans and birds, but viruses may also spread between pigs and some of them. The influenza viruses harbored by pigs in Europe are different from those harbored by pigs in Asia, for example, and when these herds meet each other, they may infect each other, and these viruses mix in their bodies and new diseases arise.

A 2016 study indicated that the movement of live pigs between Mexico and the United States and Europe provided an opportunity for the emergence of a new strain of influenza, and it infected young people who did not have antibodies to the virus, and then quickly spread around the world. The researchers stated that the live animal trade plays a big role in mixing viruses from different parts of the world with each other, and the emergence of new genetically modified species that may lead to the emergence of global pandemics.

Pigs in North America are frequently transferred from state to state. They may be bred in North Carolina and transferred to slaughterhouses in the midwestern United States near the grain farms on which they feed. “Some types of influenza are mutating at a faster rate in North America due to the movement of live pigs,” Lewis says.

China imports large numbers of live pigs to raise them or to compensate for the losses in the number of pigs due to the outbreak of disease. But by doing so, it may also import new viruses that domestic pigs have not been exposed to before, and may harm humans as well.

These practices led to an outbreak of African swine fever, which led to the death of unprecedented numbers of pigs around the world.

Pandemic into a Pandemic

In September 2020, Egbert Glaic, who works in the forestry department, received the news of the spread of African swine fever infection from Poland to the Brandenburg Forest in Germany, which extends over an area of ​​one million hectares and is inhabited by red foxes and wild boars. According to Glitch, the wild boars transmitted the disease there.

African swine fever, a highly contagious disease, may remain in the host for months. Fortunately, this disease does not affect humans, but the repercussions of its spread to pigs were severe. In 2019, reports indicate that the disease killed a quarter of the pigs in the world, including half of the pigs in China. This prompted China to increase its imports of live pigs from Brazil and Europe to compensate for the severe shortage of pork supplies due to the outbreak of African swine fever.

But African Swine Fever highlights the relationship between human activities and the diseases that humans and animals suffer.

Global warming has created ideal conditions for wild boars to breed. In the past, the cold of winter killed large numbers of wild boars, who were finding it difficult to reach their food because of the ice.

But now the winter is milder, and the wild boars have moved closer to the cities, where they have abundant food and shelter.

The animals are smart and have a high reproduction rate, and they get what they want from the city, says Sandra Blume, who runs the African Swine Fever National Reference Laboratory at the Friedrich Loeffler Institute.

Millions of wild pigs now live in Europe, and these wild pigs also act as a repository within which different viruses mix to create new viruses that may be transmitted again to other species. And large numbers of wild pigs were infected with African swine fever, and when these pigs move and mix with pigs on farms, they may infect them. And the live pigs move these viruses from one country to another.

And in Asia, where pig farms are more intensive, the disease is spread by feeding pigs with blood and the remains of dead pigs (this practice is banned in many countries). These residues are often contaminated with African swine fever.

African Swine Fever (ACF) disease appeared in Europe due to human activities. The virus, which infects feral pigs only in East Africa, was most likely brought by European colonial ships from Angola to Portugal in 1957. It appeared in Georgia in 2007 due to virus contaminated meat consumed by feral pigs. And the disease has spread throughout Russia and eastern Europe.

Although the disease does not infect humans, food remnants contaminated with the virus may kill the wild boars that feed on them within two days.

Some might argue that the solution is to get rid of wild boars in Europe. But poor hunting practices may contribute to the spread of disease, as hunters and dogs transfer contaminated blood from one place to another. And wild pigs play an important role in the ecosystem, Bloom says, by cracking the soil to provide a place for trees to grow and feed on the carcasses of other animals, and are a source of food for some predators.

The solution, Bloom says, is early detection and vaccination. With her team, she is conducting experiments to explore the response of pigs and wild boars to vaccines.

In the Blundenberg Forest, sophisticated equipment – drones, rafts and infrared monitoring devices – has been used to search for and remove infected pig carcasses.

“African Swine Fever is a highly contagious disease that quickly kills most of the affected animals. But humans contribute to spreading the disease among pigs,” said Marco Hiuritch, a participant in the team.


Although swine flu has caused physical harm to human health in the past, it is, unlike bird flu, not a reportable disease. Meaning that farmers are not legally obligated to collect samples from their pigs and submit them to government agencies for testing.

Millions depend on pig raising as their main source of livelihood. Lewis and other public health experts believe that in 2009, some farmers refrained from examining pigs to ensure they were free of disease, fearing the idea of ​​cases of the disease.

As part of the monitoring and sample collection program from pig farms, Bear and his team have so far collected a collection of new swine influenza viruses and examined their genotype and biological characteristics. They compared these viruses to the International Influenza “Epiflo” database, which contains more than a million genetic sequences of influenza viruses.

This information will allow the Bear team to understand viruses and develop vaccines against viruses that have the potential to spread to humans and cause a pandemic.

Bear says that these measures may not be sufficient to prevent a pandemic, but they will definitely help us develop a vaccine and distribute it in a shorter time in the event of an outbreak among humans.

On the other hand, the advisory board of the “IT” association for changing food production systems sent a letter to the G20, stating that the spread of intensive animal husbandry systems and agricultural practices that waste natural resources contribute to increasing the risks of virus transmission from animals to humans.

The publishers wrote: “All evidence today proves that we will not be able to recover from the Covid-19 crisis, avoid more pandemics in the future, and adhere to the sustainable development goals and the Paris Agreement, except by focusing on improving food production methods.”

When I asked Lewis about the problems that plague her now, she replied: “What worries me most now is the viruses that pigs are harboring around the world. We still lack information about these viruses.”

The more information we know about the disease, the more able we will be to prevent its spread. But we now live in an interconnected world, and it is not possible to prevent diseases in Europe from reaching Asia or diseases in Mexico from reaching the United States, and for this there will inevitably remain viruses that we do not know anything about.

Despite all the efforts made by the scientific community to prevent the transmission of viruses from animals to humans, we may need to make broader social, organizational and environmental changes to avoid a future pandemic.


Please enter your comment!
Please enter your name here