A jump in the number of people in China infected with bird flu this year is raising concern among experts, who say a previously circulating strain appears to have changed and may be more infectious to people.
China has reported 21 human infections with the H5N6 sub-type of avian influenza in 2021 to the World Health Organization, compared with only five last year. Though the numbers are much lower than the hundreds infected with H7N9 in 2017, the infections are serious, leaving many critically ill, and at least six dead.
"The increase in human cases in China this year is of concern. It's a virus that causes high mortality," said Thijs Kuiken, professor at Erasmus University Medical Center in Rotterdam.
Most of the cases had come into contact with poultry, and there are no confirmed cases of human-to-human transmission, the WHO said early this month. It added that further investigation was "urgently" required to understand the risk and the increase in spill over to people.
While human H5N6 cases have been reported, no outbreaks of H5N6 have been reported in poultry in China since February 2020.
The largest number of H5N6 infections has been in Sichuan, though cases have also been reported in Chongqing and Guangxi, as well as Guangdong, Anhui and Hunan provinces.
At least 10 were caused by viruses genetically very similar to the H5N8 virus that ravaged poultry farms across Europe last winter and also killed wild birds in China, suggesting the latest H5N6 infections may be a new variant.