The H7N9 and H7N2 avian flu viruses, which were successfully controlled by chicken vaccination, have now acquired the ability to infect ducks. Chinese scientists discovered two new types of viruses in these birds, according to an article published in the journal Cell Host & Microbe.
In September 2017, the Chinese authorities demanded the vaccination of chickens against avian influenza, which appeared in the country in 2013. Until June 2018, H7N9 infected 1,567 people, 615 of whom died. As Hualan Chen of the Harbin Veterinary Research Institute says, the vaccine was able to prevent the spread of the virus, but it could not eradicate it completely. In addition, according to scientists, since February 2018 in China there have been no cases of H7N9 avian influenza in humans.
The study authors collected more than 37,900 chicken genetic samples and more than 15,900 duck samples eight months before the introduction of mass vaccination and five months later. Before vaccination, they managed to isolate 306 varieties of the H7N9 virus, and then only 15 varieties of the H7N9 virus and one of the H7N2 virus. Most of the species found were poorly pathogenic. In only two stages of observation, the scientists found more than 1,700 viruses of different subtypes.
“I was surprised that new highly pathogenic subtypes of the virus have appeared in ducks and adapted so well to them, because the original H7N9 spreads very badly in these birds,” Chen said, quoted by the press service of the publication Cell.
Scientists have shown that in the mutation process the two varieties H7N2 and H7N9 “chose” DNA fragments from other duck flu viruses, which allowed them to infect birds better. The infected ducks were found only in the province of Fujian, however, as the article points out, some 3,000 million ducks are sold in open spaces in the markets, so a large-scale infection would be dangerous for humans.
The authors of the article assume that in the future the virus can be adapted to other types of animals. “Fortunately, our study shows that the current vaccine will work well for the ducks, so it is not necessary to develop a new one.” What we propose is to immediately start vaccinating the ducks, “Chen said.