Fear bird flu could trigger repeat of epidemic that killed 50 million

The viral proteins making up the 1918 flu strain differ by only a few molecular building blocks from those now found in bird populations around the world, scientists found.

A handful of key mutations could be all it takes to allow a 1918-like virus to spread freely between humans, according to the researchers.

They tested the ability of a reverse-engineered 1918-like virus made from components circulating in birds to transmit to ferrets, whose susceptibility to flu mimics that of humans.

“The worst-case scenario is the emergence of a novel avian influenza virus that exhibits high pathogenicity in humans, like H5N1 (avian flu) viruses, and efficient transmissibility in humans, like seasonal influenza viruses,” said lead scientist Professor Yoshihiro Kawaoka, from the University of Wisconsin-Madison.

“Our findings demonstrate the value of continued surveillance of avian influenza viruses and reinforce the need for improved influenza vaccines and antivirals to prepare for such a scenario.”

Prof Kawaoka’s team generated a flu virus composed of eight gene segments encoding proteins resembling those of the 1918 virus. All eight were in current circulation among bird populations. The resulting 1918-like virus caused illness in ferrets, and the addition of seven mutations in a few key proteins allowed it to spread efficiently from animal to animal.

A similar natural virus acquiring the same mutations could cause a human pandemic in the near future. The research, published in the journal Cell Host and Microbe, showed that the genetic ingredients for such a pandemic already exist in nature and could combine to present a potentially deadly threat.

The transmission studies were conducted in a special high containment facility at the University of Winsconsin-Madison.