WASHINGTON, June 11 (Xinhua) -- U.S. researchers said Wednesday they have used fragments of circulating avian flu viruses to successfully create a deadly flu virus that was very similar to the one that caused the 1918 pandemic, the most devastating disease outbreak ever recorded.
The study suggested a severe pandemic like the one in 1918, known as the Spanish Flu, that killed an estimated 40 million people around the world, is likely to emerge in the future, according to the researchers, led by Yoshihiro Kawaoka of the University of Wisconsin-Madison
Searching public databases, they identified eight genes from avian flu viruses isolated from wild ducks that possessed remarkable genetic similarities to the genes that made up the 1918 virus.
They used a technique called reverse genetics to generate a virus that differed from the 1918 virus by only 3 percent of the amino acids that make the virus proteins.
Tests showed that the 1918-like virus was more pathogenic in mice and ferrets that an ordinary avian flu virus, but was not as pathogenic as the 1918 virus and it did not transmit in ferrets via respiratory droplets, the primary mode of flu transmission.
However, when the 1918-like virus acquired seven amino acid mutations in a few key proteins, it spread efficiently from animal to animal, suggesting that it has the potential to cause a pandemic, the researchers said.
The resulting virus demonstrates that "the genetic ingredients for a potentially deadly and pandemic pathogen exist in nature and could combine to form such a virus," they reported in the U.S. journal Cell Host & Microbe.
"Because avian influenza viruses in nature require only a few changes to adapt to humans and cause a pandemic, it is important to understand the mechanisms involved in adaptation and identify the key mutations so we can be better prepared," Kawaoka said in a statement.
"Research findings like this help us assess the risk of outbreaks and could contribute to routine surveillance of influenza viruses," he added.
The transmission studies were conducted under specially designed high-containment conditions, using commensurate biosafety practices, at the University of Wisconsin-Madison with approval of the university's Institutional Biosafety Committee.
Previously, Kawaoka has been criticized for his creation of an altered H5N1 bird flu virus that along with similar H5N1 work by Dutch researcher Ron Fouchier sparked a year-long moratorium on the experiments two years ago.
In an article published in PLOS Medicine last month, Marc Lipsitch of Harvard University and Alison Galvani of Yale University said experiments like Kawaoka's could result in a man- made pandemic if the viruses were accidentally or deliberately released from labs.
Such experiments pose "a significant risk to public health, arguably the highest level of risk posed by any biomedical research," they wrote.
"The dangers are not just hypothetical. The H1N1 influenza strain responsible for significant morbidity and mortality around the world from 1977 to 2009 is thought to have originated from a laboratory accident," they added.