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Researchers found 72 pigs with influenza A virus.

The discovery of 72 pigs with swine influenza A virus (swIAV) in Cambodia has raised concern about the virus’ zoonotic risks.

The researchers believe that increased swine production, as well as the global trade of pigs, could increase the transmission and zoonotic capabilities of this outbreak.

The findings were discovered as part of an investigation intended to increase understanding of how influenza A viruses evolve among pigs in Southeast Asia.

Influenza A is widely recognised to cause significant morbidity and mortality amongst swine and humans. In 2009, the UK saw a swine flu pandemic that resulted in hundreds of deaths.

The virus was spread through the air, when those who were infected coughed, sneezed, breathed or talked.

The research states that influenza A viruses are a key part of the ecosystem which results in viral emergence and zoonotic diseases. Pigs especially are considered to be drivers in the emergence of influenza viruses that cross species boundaries.

In order to gain a better understanding of swIAV landscape in Southeast Asia, the researchers collected more than 4,000 nasal swabs from pigs in Cambodia between March 2020 and July 2022.

The samples were taken from 18 pig slaughterhouses in Cambodia, across four neighbouring provinces.

Analysis discovered that 72 of the pigs that were sampled tested positive for influenza A virus.

Phylogeographic reconstruction identified that south central China was the main source of swine viruses in China and Southeast Asia.

They also discovered nine swIAV lineages in Cambodia, which highlighted previously undetected diversity in the region.

This included reverse zoonoses of the human H1N1/2009 pandemic and H3N2 viruses.

The researchers say that the repeated reintroduction and reassortment of these lineages heighten the pandemic risk.

They say that the rapid growth of pork consumption, combined with the significant impact of several pig diseases including influenza and African swine fever, means that it is vital to conduct routine and sustained surveillance of pigs to identify new viruses and their zoonotic risks.

They state that current methods of disease surveillance are not fit for purpose, and better methods are needed to monitor zoonotic risks.

The research was conducted by researchers at the Duke-National University of Singapore Medical School, the London School of Hygiene and Tropical Medicine and the National Animal Health and Production Research Institute in Cambodia.

The full study can be found in the Proceedings of the National Academy of Sciences journal.

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