Scientists recently discovered that a new strain of the bird flu virus can resist first-line treatment drug and is able to spread in mammals, according to a Reuters report.

Unlike common flu that becomes less transmissible when treated, the new findings said that the new H7N9 bird flu does not lose its potential spreading ability even if treated with appropriate drugs, the report said.

However, scientists say that the H7N9 will not likely lead to a human pandemic. Researchers said that the discovery will help doctors be more prudent when treating H7N9 cases.

"It's important to emphasize that these H7N9 viruses seem to transmit fairly inefficiently overall," said Nicole Bouvier, who led the H7N9 study published in the journal Nature Communications on Tuesday, December 10.

Bouvier and her colleagues were surprised that the new strain of bird flu is not as efficient as the first strain. "Usually, what we see with influenza is that resistance... also confers a fitness disadvantaged on the virus," she said.

Bouvier's team, the Mount Sinai School of Medicine in New York, analyzed a sample of the new strain from an infected patient in China to determine if the virus is infectious. They found that the virus resisted Tamiflu, a first-line treatment developed by Roche, but continue to show signs of transmissibility. Tamiflu, known generically as oseltamivir, is used for treating flu infections. The virus spread between laboratory animals.

"This is unusual, as it is known that when seasonal influenza viruses gain resistance to drugs, it usually happens at a cost to the virus - the cost being a reduced ability to transmit between hosts and to grow within them," the team wrote.

H7N9 bird flu emerged in China earlier this year and has infected at least 139 people in places like China, Taiwan and Hong Kong, killing 45 of them.