Researchers study Influenza D in pigs to assess human spillover risk

The influenza D virus that researchers say has been flying under the radar since its detection in animals in 2011 can vigorously make copies of itself in human cells and lung tissue samples, a new study shows.

The findings suggest influenza D has strong potential to spill over to humans, the scientists say. Some people who work with cattle, considered the primary host for this virus, have been found to have influenza D antibodies in their blood, but no active human infection has been discovered to date.

Results showed that several genetically different strains of influenza D that were isolated from cattle and pigs, another animal host, were as effective at replicating in cells from the human respiratory tract as influenza A viruses – the types of flu linked to both modern seasonal illness and historic pandemics.

“All of the viruses, despite their genetic distance from each other, had similar replicative capacity in these human cells and human tissues,” said lead author Cody Warren, assistant professor of veterinary biosciences at The Ohio State University. “It seems like there are many animal species that are susceptible to influenza D viruses, suggesting that maybe they can evolve differently in different hosts. What’s obvious is that zoonotic infections are happening. This is an opportunity, if we are indeed in front of it, to invest in surveillance and basic understanding of its biology such that we could be prepared if it were to emerge in the future.”