A virus first identified in a US pig has officially been named influenza D by the International Committee of Taxonomy of Viruses, according to South Dakota State University (SDSU) researchers involved in the discovery of the pathogen. The virus does not seem to pose a major threat of crossing over to humans, but scientists worry that influenza D could acquire DNA from a virus that can.

The virus was discovered in a pig in Oklahoma in 2011. However, influenza D has proven to be more of a problem for cattle. The virus now circulates in French cattle herds. The Centers for Disease Control analyzed the genetic code of influenza D from French outbreaks. The scientists found that the DNA was 95 to 99 percent similar to US types, which suggests the disease spread across the ocean.

Discovery of influenza D

This is the first influenza virus identified in cattle, said SDSU professor Feng Li in a press release. SDSU alumnus Ben Hause isolated the virus from a diseased pig then found that cattle were the primary reservoir for influenza D.

Li and Radhey Kaushik, professor of biology and microbiology, secured a National Institutes of Health grant for nearly $400,000 to study the virus.


Ultimately, the goal is to determine whether influenza D, which has 50 percent similarity to human influenza C, can cause problems in humans, according to Kaushik. However, he noted, “the virus has not been shown to be pathogenic in humans. No one should be afraid of this.”

The research group showed that influenza D is spread only through direct contact and proved a guinea pig can be used as an animal model to study the virus. Influenza D antibodies have been identified in blood samples from sheep and goats, but the virus does not affect poultry.

Spread to humans

Studies are underway to compare the virulence among the bovine and swine influenza D strains and human influenza C using the guinea pig model.

“If the virus can undergo reassortment in combination with a closely related human influenza virus, it may be able to form a new strain that could pose more of a threat to humans,” Kaushik said.