Flu Severity Varies by Virus Subtype

Certain flu virus subtypes have more potential to cause severe illness than others, according to a new study published in mBio. For that reason, avian influenza viruses that express the more dangerous subtypes should be monitored closely to prevent the spread of severe disease.

Jeffery Taubenberger, MD, PhD, chief of the Viral Pathogenesis and Evolution Section of National Institute of Allergy and Infectious Diseases’ Laboratory of Infectious Diseases, worked with a research team to mimick 13 subtypes of contemporary pathogenicity avian influenza A viruses. In doing so, the researchers discovered that the viruses expressing the H1, H6, H7, H10, and H15 subtypes caused weight loss and fatal pneumonia in mice within 1 week, while those expressing the H2, H3, H5, H9, H11, H13, H14, and H16 subtypes did not.

"Viruses with these avian hemagglutinins have some type of inherent virulence motif to them, in that they induce a marked inflammatory response in mammals including human cells in culture," Dr. Taubenberger said in a press release. "From a public health and epidemiology standpoint, it's useful to know that avian viruses of these subtypes (for example, H6, H7, or H10) might lead to more severe infections in humans and is something to look out for."

For instance, the researchers noted that the H1-expressing virus was a key virulence factor in the 1918 “Spanish flu” pandemic that resulted in approximately 50 million deaths.

Dr. Taubenberger called for more research to determine how flu viruses spread from animals to humans, which he said would aid in the production of a “universal” influenza vaccine that could better protect against future pandemics.