TAIPEI (Taiwan News) — The World Health Organization (WHO) has said further investigation is "urgently" needed to understand the increase in human transmission of bird flu in China.
Experts say a strain of the disease appears to have mutated and may be more infectious to people, citing a jump in the number of people in China infected with bird flu so far this year.
China has reported 21 human infections with the H5N6 subtype of avian influenza to the WHO in 2021 compared to only five last year, according to a Reuters report.
The infections are serious and have left many critically ill and at least six dead, though numbers are much lower than the hundreds infected with H7N9 — another type of avian influenza — in 2017.
"The increase in human cases in China this year is of concern. It's a virus that causes high mortality," said Thijs Kuiken, professor of comparative pathology at Erasmus University Medical Centre in Rotterdam.
Most cases had come into physical contact with poultry, and there are no confirmed cases of human-to-human transmission, said the WHO, which referred to the rise in cases in a statement earlier this month.
Since then, a 60-year-old woman in Hunan Province was rushed to hospital in critical condition with H5N6 influenza on Wednesday (Oct. 13), per the Hong Kong government.
While human H5N6 cases have been reported, no outbreaks of H5N6 have been reported among poultry in China since February of last year.
China is not only the world's biggest poultry producer but also the top producer of ducks, which can serve as a reservoir for flu viruses, per Reuters.
The Chinese Center for Disease Control and Prevention (CDC) published a statement on its website last month saying the "increasing genetic diversity and geographical distribution of H5N6 pose a serious threat to the poultry industry and human health.”
Avian influenza viruses constantly circulate in domestic and wild birds but rarely infect people. However, the evolution of the viruses, which have increased as poultry populations grow, is a major concern because they could change into a virus that spreads easily between people and cause a pandemic.
At least 10 of the H5N6 infections were caused by viruses with very similar genetic properties to the type of H5N8 that cut through poultry farms across Europe last winter and killed wild birds in China, which suggests the latest H5N6 infections in China may be a new variant, per reports.
"It could be that this variant is a little more infectious (to people)... or there could be more of this virus in poultry at the moment and that's why more people are getting infected," said Kuiken.
Though China vaccinates poultry against avian influenza, the vaccine used in 2020 may only partially protect against emerging viruses, which can stop large outbreaks but allows the virus to continue circulating, said Filip Claes, regional laboratory coordinator at the Emergency Centre for Transboundary Animal Diseases at the Food and Agriculture Organization.
China’s Ministry of Agriculture and Rural Affairs did not respond to Reuters' request for comment on the issue.