RACHEL MARTIN, HOST:
A strain of bird flu has been found on a farm in Tennessee. Officials say there's no risk to the food supply. And more than 70,000 birds will be culled. It's the first confirmed case of the H7 strain of bird flu in American commercial poultry this year. In China, though, there's been a surge of human infections with a separate strain of avian flu. It's the H7N1 strain, rather H7N9 strain. NPR's Rob Schmitz reports from Shanghai.
ROB SCHMITZ, BYLINE: Four hundred and sixty people in China have been infected by the H7N9 strain of the bird flu this year. A third of them have died. This makes 2017 a record year for human infections of the virus. Scientists are trying to figure out why. Dr. Chin Kei-Lee is a medical officer for the World Health Organization in Beijing.
CHIN KEI-LEE: So far, what we have monitored haven't found any changes that can suggest any change in the human-to-human transmission or making human more sick.
SCHMITZ: In other words, scientists don't have evidence that the virus has gotten worse for humans. There is new evidence to suggest though that it's gotten worse for birds, a mutation of the H7N9 strain has made the virus more deadly in infected birds, especially chickens. This threatens to impact a global poultry industry worth hundreds of billions of dollars. And it raises questions about how future mutations will impact humans.
As a precaution, American scientists are developing an H7N9 vaccine from which an emergency stockpile could be drawn if the virus should become more lethal and transmissible among humans. Rob Schmitz, NPR News, Shanghai.
(SOUNDBITE OF ZHAO CONG, HANS NIELSEN'S "SONGS OF HORSE HERDING")
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