New flu gene found hiding in plain sight, and affects severity of infections

“This is indeed an exciting finding in the flu field,”

I could write the entire genome of a flu virus in around 100 tweets. It is just 14,000 letters long; for comparison, our genome has over 3 billion letters. This tiny collection of genetic material is enough to kill millions of people. Even though it has been sequenced time and time again, there is still a lot we don’t know about it.

A new study beautifully illustrates the depths of our ignorance. Brett Jagger and Paul Digard from the University of Edinburgh have discovered an entirely new flu gene, hiding in plain sight among the 12 we knew about. It’s like someone took the text of Macbeth, put the spaces in different places, and got Hamlet.

This new gene, known as PA-X, affects how the virus’s host responds to the virus. Oddly, it seems to reduce the severity of infections. “This is indeed an exciting finding in the flu field,” says virologist Ron Fouchier. “How can we have missed it?” asks Wendy Barclay, a flu researcher from Imperial College London who has worked with Digard before. “It just emphasizes how compact these genomes are.”

Most influenza viruses belong to the influenza A group – these are the ones behind all the big pandemics, the seasonal strains that sweep the world every year, and the mutant strains that have caused such a stir recently. Each influenza A virus is a shell containing eight strands of RNA, a genetic molecule related to DNA. But some of these strands encode multiple genes, each of which produces a different protein. Until recently, we thought that the eight strands contain 12 different genes, and the new study raises that number to 13. The influenza genome, it turns out, is absolutely packed with overlapping instructions.