Bird flu: Scientists find mutations, say threat is still low

A man in Chile is infected with a bird flu that has concerning mutations, but the threat to people from the virus remains low, U.S. health officials said Friday.

A man in Chile is infected with a bird flu that has concerning mutations, but the threat to people from the virus remains low, U.S. health officials said Friday.

Past animal studies suggest these mutations could cause the virus to be more harmful or spread more easily, health officials said. But they also said there is no evidence that the mutations would make it easier for it to take root in a person's upper lungs -- a development that would raise concerns about spread among people.

The mutations do not change public health officials' assessment of the overall risk to people from the H5N1 virus, which "continues to be low," said Vivien Dugan of the Centers for Disease Control and Prevention.

The mutations, which have appeared only in the one hospitalized patient, may have occurred after the man got sick, CDC officials said. There's no evidence that the mutated virus spread to other people, mixed with other flu viruses, or developed the ability to fight off current medicines or evade vaccines, agency officials said.

Such genetic changes have been seen in past bird flu infections.

"Nevertheless, it's important to continue to look carefully at every instance of human infection," Dugan said. "We need to remain vigilant for changes that would make these viruses more dangerous to people."

This type of flu, called Type A H5N1, was first identified as a threat to people during a 1997 outbreak in Hong Kong, when visitors to live poultry markets caught it.