WEDNESDAY, March 11, 2015 (HealthDay News) -- Avian flu, commonly called "bird flu," is gaining strength in China and has the potential to emerge as a life-threatening virus for humans across the globe, a new report suggests.
In the year since avian flu first surfaced in China, it has expanded throughout that country and become a persistent infection in chickens there, the new report states.
The virus also has begun to mutate in chickens, raising concerns that it could gain the ability to more easily infect humans and spread beyond China, the study authors warned.
"Therefore, H7N9 viruses should be considered as a major candidate to emerge as a pandemic strain in humans," Yi Guan, from the University of Hong Kong, and colleagues concluded in the March 11 issue of the journal Nature.
Avian flu, also known as H7N9 influenza, first appeared in eastern China in March 2013 when the virus spread to humans from infected poultry, according to the U.S. Centers for Disease Control and Prevention.
A second wave of the H7N9 outbreak that began in late 2013 has resulted in at least 318 human infections and more than 100 deaths -- more than twice that of the first wave, the study authors said.
To better understand this second wave and predict its path, researchers monitored the evolution and spread of H7N9 over 15 cities across five provinces in China.
The researchers identified a large number of new genetic variants that have become established in chickens, and tracked the march of those viral mutations across the country as chickens were sold and transported.
"With the recent reports of H7N9 infections in Xinjiang in the far northwest of China, it is probable that the H7N9 virus is now present across most of China," the study authors wrote. "As this virus does not cause obvious symptoms in chickens and only limited surveillance has been conducted, the prevalence of this virus is likely to be higher than we document here," they added.
U.S. infectious disease experts said the new report out of China raises serious concerns.
"Yes, we should be worried," said Dr. Trish Perl, an infectious disease expert at Johns Hopkins Medicine in Baltimore. "The story they tell is extremely compelling. They show this avian flu almost marching through different regions in China."
Dr. Bruce Hirsch, an infectious diseases specialist at North Shore University Hospital in Manhasset, N.Y., added that "influenza viruses recombine, evolve and develop new strains continuously. This virus appears widespread in bird populations. And we wonder if this flu could be 'the big one,' repeating the great flu outbreak of 1918, which caused 100 million deaths worldwide."
The study authors propose measures that can be taken to slow or halt the spread of the avian flu. These include permanently closing all live poultry markets, halting the transportation of poultry between regions during a disease outbreak, and shutting down large poultry slaughtering plants.
According to Dr. Robert Glatter, an emergency physician with Lenox Hill Hospital in New York City, "Unless swift measures to control the spread of H7N9 are put into place, there could be a major spread of the virus throughout China and the rest of Asia."
And, Glatter added, "with the ease of air travel, it is possible that the virus could even make it to Europe and the United States."
Ellen Silbergeld is a professor of environmental health sciences at the Johns Hopkins Bloomberg School of Public Health in Baltimore. She said that officials in China also need to improve their surveillance of H7N9 in chickens at large poultry houses.
Silbergeld believes that big poultry houses likely pose an even greater threat than live poultry markets for the spread of avian flu. She suggested that the ventilation systems in the big facilities allow for easy spread of the virus between chickens.
"A lot of the programs are still designed to give a free ride to the large-scale chicken industry, because it's 'confined,'" which allegedly prevents chickens from catching viruses from other passing birds, Silbergeld said.
"But all of the houses are very heavily ventilated, and the ventilation system is the Achilles' heel," she continued. "The modern industrial poultry production is actually worse, because it's not really contained and it's got so many more organisms, providing a playground for viral evolution."
However, Perl pointed out that humans have one new advantage -- improved genetic sequencing technology that has revolutionized epidemiology and made studies like this possible.
"The technology at use in this setting is going to be extremely powerful in helping us understand emerging infectious diseases," Perl said. "Now we need to develop surveillance systems that cross-communicate with humans as well as animals and are global. We need to leverage these techniques so we can put into place appropriate prevention measures."
Visit the U.S. Centers for Disease Control and Prevention for more on the H7N9 flu virus.
SOURCES: Trish Perl, M.D., M.Sc., infectious disease expert, Johns Hopkins Medicine, Baltimore; Bruce Hirsch, M.D., infectious diseases specialist, North Shore University Hospital, Manhasset, N.Y.; Robert Glatter, M.D., emergency physician, Lenox Hill Hospital, New York City; Ellen Silbergeld, Ph.D., professor, environmental health sciences, Johns Hopkins Bloomberg School of Public Health, Baltimore; March 11, 2015, Nature