Shoppers in Hangzhou wear face masks as a precaution against H7N9. (Photo/CNS)

The new H7N9 strain of avian influenza that has so far killed six people and left another 15 critically ill in eastern China has the basic genetic hallmarks of an easily transmissible virus, according to a virology expert.

Ron Fouchier, a professor of molecular virology at Erasmus Medical Center in the Netherlands, told Bloomberg on Saturday that the H7N9 subtype was formed from two viruses merging their genetic material. Adding that the new strain of bird flu has features of viruses that are known to jump easily from birds to mammals, and a mutation that may help it attach to cells in the respiratory tract.

"That's certainly not good news," he said after reviewing a gene sequencing of H7N9 published by Chinese health authorities.

Last year, Fouchier studied the H5N1 subtype of the avian flu, the strain that sparked the previous outbreak in Asia in 2003 that has so far killed more than 600 people in a dozen countries. After implementing five genetic tweaks, Fouchier showed that the virus could become transmissible by air to ferrets, the mammal that responds to influenza closest to humans.

Two of the mutations Fouchier made are present in H7N9, leading him to conclude that it is "certainly of more concern than the vast majority of bird flu viruses." While it is not clear whether these mutations alone can make the virus easily transmissible, the possibility is something that should be investigated, he said.

While there is currently no evidence that the H7N9 virus can spread between humans, the possibility has not been ruled out by scientists, who continue to scrutinize the strain for more clues. As a precaution, live poultry trading has been suspended in the cities of Shanghai, Nanjing and Hangzhou.

Fouchier does not believe that a pandemic is imminent, however, pointing to the fact that H5N1 has circulated for 16 years and has not become mammal-to-mammal transmissible.