Summary of “Swine Flu” Strain Has Passed From Humans to Pigs Nearly 400 Times Since H1N1 Pandemic:
A new study published in PLOS Pathogens has found that the strain of influenza A responsible for the 2009 H1N1 pandemic, known as pdm09, has passed from humans to swine approximately 370 times since 2009. This circulation in swine has resulted in the evolution of pdm09 variants that have then crossed back to infect humans. The researchers analyzed transmission data from 2009 to 2021 and found that most human-to-swine transmission events occurred when the pdm09 burden was highest among humans. During the COVID-19 pandemic, pdm09 circulation among humans dropped but persisted in swine due to human-to-swine transmissions. The study also identified instances where swine-circulating pdm09 variants were genetically poor matches for human seasonal vaccines, indicating limited protection. These findings highlight the importance of managing influenza A infection in people who work with swine to prevent transmission to pigs and reduce the risk of spread back to humans.
Summary:
1. The pdm09 strain of influenza A, responsible for the 2009 H1N1 pandemic, has passed from humans to swine approximately 370 times since 2009.
2. The circulation of pdm09 in swine has resulted in the evolution of variants that can jump back to humans.
3. These findings highlight the importance of managing influenza A infection in people who work with swine to prevent transmission to pigs and reduce the risk of spread back to humans.
The transmission of influenza A virus between humans and animals is a well-known phenomenon. In recent years, researchers have been closely monitoring the transfer of the pdm09 strain of influenza A, responsible for the 2009 H1N1 pandemic, between humans and swine. A new study published in the open-access journal PLOS Pathogens sheds light on the frequency of these transmissions and their impact on the genetic diversity of the virus.
According to the study, the pdm09 strain has passed from humans to swine approximately 370 times since 2009. This highlights influenza viruses’ dynamic nature and ability to cross species barriers. Most of these transmission events occurred when the pdm09 burden was highest among humans, emphasizing the importance of human-to-human transmission in driving subsequent transmissions to swine.
Interestingly, the COVID-19 pandemic had a notable impact on the circulation of pdm09. While pdm09 circulation among humans dropped during the pandemic, it persisted in swine due to around 150 human-to-swine transmissions between 2018 and 2020. This highlights the resilience of pdm09 in swine populations and its potential to continue evolving.
The study also found that some human-to-swine transmission events led to the sustained circulation of different pdm09 genetic lineages among swine in the United States. These variants appeared to be genetically distinct from the strains in human seasonal vaccines, suggesting they may not have provided optimal protection against them. This highlights the importance of continuously monitoring the genetic diversity of influenza viruses in swine populations to inform vaccine development efforts.
Importantly, the analysis also revealed that persistent pdm09 circulation among swine was associated with at least five instances of swine-to-human transmission. This demonstrates the risk of these transmissions and the potential for pdm09 to jump back to humans, leading to further outbreaks or pandemics.
These findings further support the need to manage influenza A infection in people who work with swine. BMinimizing the virus’s spillover into pigs can reduce the diversity of viruses circulating in swine populations. This, in turn, can minimize the emergence of novel viruses and the potential for swine-to-human transmission of influenza A viruses.
In conclusion, the study highlights the ongoing transmission of the pdm09 strain of influenza A between humans and swine. The dynamic nature of influenza viruses and their ability to cross species barriers underscores the importance of proactive measures to manage influenza A infection in individuals working with swine. Understanding the genetic diversity of influenza viruses in swine populations is crucial for informing vaccine development and reducing the risk of future outbreaks or pandemics.
