Influenza D in Horses

       This year a lot of media coverage has focused on influenza. The flu, which sickens more than 1 billion people annually comes in four distinct strains, influenza A, B, C and D. Within each strain of the flu there are different variants of the Haemaglutanin and Neuraminidase envalope proteins that envoke novel immune system detection to the disease each year. 
   In humans the most common strains of influenza are influenza A and B.  Influenza D actually was discovered fairly recently, in pig populations in 2011.  The big worry with animal influenza is that it will cross over into human populations so a lot of work is done to survey flu in animal hosts.  By conducting in depth animal surveillance we know which populations of humans are most vulnerable to also getting the disease.   When it comes to influenza D, researchers found that the main animal host of the disease is not actually pigs, but cows.
     Last week, a report coming out of South Dakota State expanded the scientific community's knowledge on influenza D even more. This study reported that the the disease is actually found in horses as well.  The study tested 364 horses for influenza D and found that 12% of them had symptoms of the disease.  Since humans ride horses this means that there be an even greater increased risk of spillover from horse populations to humans than cow populations. 

- Chris LeBoa
<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5766371/>