ATLANTA - As the U.S. flu season winds down, scientists in the Centers for Disease Control and Prevention's Atlanta flu lab are focused on finding the next pandemic flu threat.
And they're watching a deadly strain of bird flu in China.
"There are features of this strain that are worrisome," says CDC Acting Director Dr. Anne Schuchat.
She's talking about the H7N9 bird flu, which began spreading from poultry to people in 2013, with lethal consequences.
"And while this is the fifth year of seeing the disease, this year has been worse than any of the previous ones in China," Dr. Schuchat says.
So far, in the fifth outbreak alone, the World Health Organization says 623 people have been sickened.
That brings the total of lab-confirmed H7N9 infections to 1,421 since 2013.
Most of those infected had been exposed to poultry, but there were some rare cases of limited person-to-person spread.
This virus moves quickly, progressing from high fever and cough to severe breathing complications like pneumonia.
The WHO says up to 40 percent of those infected die.
"When a new influenza strain it emerges, it is a risk from being spread easily from person to person," Dr. Schuchat says. "This one hasn't done that yet. But that's why we're keeping our eye on it. Because it has the capacity to evolve and change."
And that change is already happening.
The CDC had developed an H7N9 vaccine using earlier circulating strains of the virus. But Schuchat says they started seeing signs the flu has mutated, becoming more deadly in birds, and, they think, more resistant to the drugs we use to treat influenza.
"And when we got the strains and could actually look at them, what we see is that they have changed," Schuchat says. "So, they have developed away from the vaccine that was developed against this H7N9 strain into something that we need to attend to."
Now, with a surge in new infections, CDC scientists have gone back to the vaccine drawing board.
"Our scientists are taking that strain from the new bird flu viruses and making a candidate vaccine virus that can be used to hand off to companies, so that the flu vaccine manufacturers can make a new vaccine against that bird flu strain."
It could take months to develop a just-in-case vaccine.
But, Dr. Schuchat says, the good news is this virus has not learned yet to spread easily, which is a feature of pandemic flu.
So the risk of a worldwide outbreak, or pandemic flu, remains low.
"But we can never be complacent about the risk for new threats," Dr. Schuchat cautions. "We know that Ebola in West Africa seemed very far away to people, until it was on our doorstep here in Atlanta."
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