August 2023

In a recent study shedding light on the dynamics of influenza A strains, researchers discovered that the H1N1 strain responsible for the 2009 pandemic has crossed between humans and swine around 370 times since its emergence.

The findings underscore the ongoing risk of interspecies transmission and subsequent evolution of the virus, potentially leading to new outbreaks among humans. As influenza A viruses can infect a range of animals, including humans, birds, swine, and certain mammals, understanding interspecies transmission is crucial for pandemic prevention.

The H1N1 strain, known as pdm09, caused a global pandemic in 2009 and 2010, resulting in 151,700-575,400 deaths globally according to the CDC. The study’s analysis of transmission data between 2009 and 2021 revealed that the virus has repeatedly jumped between humans and swine.

While most instances of human-to-swine transmission were isolated, some led to sustained circulation of pdm09 variants in swine populations. These variants were genetically distinct from strains targeted by human seasonal vaccines, indicating limited vaccine efficacy against them.

There is a strong focus to manage influenza A infection in people who work directly with swine. By managing human infections, the spillover of viruses into pig populations can be minimized. This, in turn, reduces the diversity of viruses circulating among swine, thereby mitigating the emergence of novel strains that could potentially transmit back to humans.

If you are interested in learning more about influenza A or our other in house viruses, please contact Karen Ramm at [email protected].