Spanish Flu-Like Virus Found in Nature can Potentially Kill Millions

An international team of researchers has shown that avian influenza viruses currently circulating in nature contain all the genetic ingredients necessary to create a Spanish flu-like pandemic, and could potentially kill millions.

University of Wisconsin-Madison researchers recently identified eight genes from influenza viruses isolated from wild ducks that possessed remarkable genetic similarities to the genes that made up the 1918 pandemic flu virus, commonly known as the "Spanish flu."

This pandemic was one of the most devastating outbreaks of disease ever recorded in history, resulting in an estimated 40 million deaths worldwide.

For another disease of similar epic proportions to devastate the human population in such a way would be catastrophic.

In a press release, lead author Yoshihiro Kawaoka explained that "there are gene pools in nature that have the potential to cause a severe pandemic in the future."

To assess how much of an immediate risk these eight 1918-like genes posed, the team used reverse genetics methods to generate a virus that was nearly identical to the Spanish flu virus. Luckily, the genetically modified virus did not exhibit characteristics of pandemic capabilities, for when they tested the virus in ferrets, it did not transmit via respiratory droplets - the primary mode of flu transmission.

However, researchers were curious how many alterations it would take before the virus could become transmittable. They ultimately identified seven mutations in three viral genes that enabled the pathogen to transmit as efficiently as the 1918 virus. The resulting virus, composed of genetic factors circulating in wild and domesticated birds, demonstrates that the genetic ingredients for a potentially deadly and pandemic pathogen exist in nature and could combine to form such a virus, according to Kawaoka.

The new study is important because it shows the potential risk of circulating strains of avian influenza viruses, Kawaoka explains. Knowing what genes to look for, he says, can help predict the likelihood of an emerging strain of pandemic flu and, more importantly, help scientists devise strategies for countering such a pathogen.

"With each study, we learn more about the key features that enable an avian influenza virus to adapt to mammals and become transmissible," he added. "Eventually, we hope to be able to reliably identify viruses with significant pandemic potential so we can focus preparedness efforts appropriately."

The new work was published today in the journal Cell Host and Microbe.