In China, a deadly strain of bird flu now easily infects ducks

A vaccine that protects chickens from the virus works in ducks, too

ducks in China

DUCK FLU Some ducks in China’s Fujian province carry highly pathogenic strains of the H7N9 avian influenza virus. The ducks shown here were photographed on a farm in Fujian province in April 2013, three years before the high pathogenicity strains emerged.

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Some ducks in China now carry a deadly strain of bird flu.

Highly pathogenic versions of H7N9 — a bird flu strain that’s proven particularly deadly to people — and H7N2 viruses have turned up in ducks in the Fujian province. These viruses replicate easily in the ducks and can kill them, researchers report September 27 in Cell Host & Microbe. The discovery is worrisome because the virus made the jump to ducks just ahead of efforts to eliminate H7N9 by vaccinating chickens.

Since H7N9 began sickening people in 2013, a total of 1,625 people have contracted the bird flu strain and 623 have died. Most of those infected had been in contact with chickens (SN Online: 3/11/15). Initially the virus killed about a third of people who caught it. But in 2016, the virus mutated to become even deadlier in both poultry and people, killing about half of people it infected.

A vaccine against the virus protects chickens, and consequently people, the new study found. No human cases of H7N9 have been reported since October 2017.

But ducks weren’t vaccinated because the original H7N9 virus didn’t infect them easily.

Now, they should be to prevent the deadlier virus strains from spreading to other poultry, wild birds and to people, the researchers write.

Tina Hesman Saey is the senior staff writer and reports on molecular biology. She has a Ph.D. in molecular genetics from Washington University in St. Louis and a master’s degree in science journalism from Boston University.

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