For the past three years we've been following the discovery, and research into, a new type of influenza - first isolated in swine in 2011 and initially classified as a novel Influenza C virus - but since that time has been found to be endemic in cattle and tentatively proposed as being a new `Type D' Influenza virus.
The first study - published PLoS Pathogens – was called Isolation of a Novel Swine Influenza Virus from Oklahoma in 2011 Which Is Distantly Related to Human Influenza C Viruses, and it immediately caused a stir in the flu research community.
Of note, the authors found that this new (provisional) influenza C virus could infect, and transmit, in both ferrets and pigs. The authors described this new discovery as:
. . . a new subtype of influenza C viruses that currently circulates in pigs that has not been recognized previously. The presence of multiple subtypes of co-circulating influenza C viruses raises the possibility of reassortment and antigenic shift as mechanisms of influenza C virus evolution.
A little over two years ago, in mBio: Characterizing A Novel Influenza C Virus In Bovines & Swine we looked at a second paper by these same researchers, which added cattle to the list of hosts found to carry this novel virus.
Last April, in JVI: Pathogenesis Of Influenza D in Cattle, we saw even more evidence that cattle are the natural reservoir for Influenza D, while this past June we saw Serological Evidence Of Influenza D Among Persons With & Without Cattle Exposure.
This serological study, published in the Journal of Clinical Virology, found:
IDV poses a zoonotic risk to cattle-exposed workers, based on detection of high seroprevalence (94–97%). Whereas it is still unknown whether IDV causes disease in humans, our studies indicate that the virus may be an emerging pathogen among cattle-workers.
Which brings us to an announcement, from South Dakota State University, that the International Committee of Taxonomy of Viruses has approved the naming for this emerging virus to Influenza D, as proposed by two of their researchers.
It’s official. The executive committee of the International Committee of Taxonomy of Viruses approved naming a new virus, influenza D, as the South Dakota State University researchers who discovered it proposed, according to professor Feng Li. The committee officially announced a new genus, Orthomyxovirdae, with a single species, Influenza D virus, because of its distinctness from other influenza types—A, B and C.
Though SDSU alumnus Ben Hause isolated the virus from a diseased pig in 2011, he later found that cattle were the primary reservoir for influenza D. Hause identified and characterized the new virus as part of his doctoral research under Li’s tutelage.
This is the first influenza virus identified in cattle, Li explained. “This contribution was made in South Dakota and our theory has been confirmed independently by other research groups.”
Li and Radhey Kaushik, professor and assistant head of the biology and microbiology department, secured a National Institutes of Health grant for nearly $400,000 to study the biology, genetics and evolution of the new virus.
(Continue . . . )
Our understanding of the host range, diversity, and ecology of influenza viruses grows every year.
- Dogs were only added to the list of hosts in 2004, and until tigers began dying of H5N1 in Thailand, cats were believed relatively immune to the flu (see A Dog & Cat Flu Review).
- In 2012 bats were found to carry novel (H17 & H18) flu viruses
- And just last month, in Emerg. Microbes & Inf.: Prevalence Of Influenza A in North Atlantic Gray Seals, we saw a study that raised the intriguing possibility that Gray Seals might be a natural wild reservoir for the virus as well.
While the public health impact of these discoveries are uncertain, each one is a reminder of how much more there is for us to learn about a virus that kills - in an average year - 500,000 people, and on very rare occasions, can claim the lives of tens of millions.