Bird flu's mutating in China raises alarm

A woman and daughter are frightened by ducks approaching for food at a Beijing park. Scientists say the new flu strain could be harder to track because it seems to spread among poultry without making them sick. It also seems capable of infecting pigs.
A woman and daughter are frightened by ducks approaching for food at a Beijing park. Scientists say the new flu strain could be harder to track because it seems to spread among poultry without making them sick. It also seems capable of infecting pigs. (AP)

Nine people are sickened and three dead. Tests continue.

Posted: April 05, 2013

BEIJING - In a worrisome sign, a bird flu in China appears to have mutated so that it can spread to other animals, raising the potential for a bigger threat to people, scientists said Wednesday.

So far, the flu has sickened nine people in China and killed three. It's not clear how they became infected, but there's no evidence the virus is spreading easily among people.

But the virus can, evidently, move through poultry without making them sick, experts said, making it difficult to track the germ in flocks. The findings are preliminary and need further testing.

In the wake of the illnesses, the Chinese Center for Disease Control and Prevention shared the genetic sequence of the H7N9 virus with other scientists to help study how the virus might behave in different animals and situations.

One scientist said that the sequence raised concern about a potential global epidemic, but that it was impossible to give a precise estimate of how likely that is.

"At this stage, it's still unlikely to become a pandemic," said Richard Webby, director of a World Health Organization flu center at St. Jude Children's Research Hospital in Memphis, Tenn.

The virus has genetic markers that would help it infect people, Webby said. That makes him worry about a pandemic a bit more than he does for other bird flu viruses, he said, such as the H5N1 virus that emerged a decade ago.

"The tentative assessment of this virus is that it may cause human infection or epidemic," said Masato Tashiro, director of the WHO's influenza research center in Tokyo and one of the specialists who studied the genetic data. "It is still not yet adapted to humans completely, but important factors have already changed."

Flu viruses evolve constantly, and scientists say such changes have made H7N9 more capable of infecting pigs.

Pigs are a particular concern because bird and human flu viruses can mingle there, potentially producing a bird virus with heightened ability to spread between humans, said William Schaffner, a flu expert at the Vanderbilt University School of Medicine. That's what happened in 2009 with swine flu.

If there are no obvious symptoms in birds or pigs, "nobody recognizes the infection in animals around them," Tashiro said. "In terms of this phenomenon, it's more problematic."

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