Two new types of bird flu infections currently spreading in China could jump to humans threatening global health, scientists warn.

The avian influenza virus subtype H16N3, first identified in 1975 and currently detectable among wild birds in many countries, has so far not posed a threat to humans so far.

But a team of researchers from State Key Laboratory of Veterinary Biotechnology in Harbin, China, have isolated two H16N3 subtype influenza viruses that can bind to both human and avian-type cell receptors, according to findings published in Transboundary and Emerging Diseases^[1]https://onlinelibrary.wiley.com/doi/10.1111/tbed.13511.

The team led by Li Yulei also found evidence that genetic material from other species has been introduced into the H16N3 avian influenza virus, which suggests that it may infect other species and could therefore pose a threat to animal and human health in the future.

The findings come after the scientists carried out extensive surveillance of the H16N3 subtype of bird flu in large gatherings of wild birds in China from 2017 to 2019.

“Segments from other species have been introduced into the H16N3 avian influenza virus, which may alter its pathogenicity and host tropism, potentially posing a threat to animal and human health in the future,” the researchers wrote. “Consequently, it is necessary to increase monitoring of the emergence and spread of avian influenza subtype H16N3 in wild birds.”

Animal influenza viruses are distinct from human seasonal flu viruses and do not easily spread from human to human.

But some zoonotic influenza viruses – animal influenza viruses that have jumped species and infect humans – cause disease in people ranging from a mild illness to death.

The most recent case of a zoonotic virus is the SAR-CoV-2 coronavirus, which is responsible for the COVID-19 pandemic that began in Wuhan, China, and has spread worldwide so far infecting 1.8 million people and claiming more than 113,000 lives^[2]https://gisanddata.maps.arcgis.com/apps/opsdashboard/index.html#/bda7594740fd40299423467b48e9ecf6.

The COVID-19 pandemic has wreaked havoc on the global economy and overwhelmed healthcare systems in a number of countries including the United States.

China has emerged as ground zero for zoonotic pandemic outbreaks due to the prevalence of so-called wet markets where live animals – including endangered wild species – are sold for food.

The A(H5N1) virus spread around the world following a bird flu outbreak in Hong Kong, China in 1997 and human infections with the influenza A(H7N9) virus were reported in China in 2013, according to the World Health Organization ^[3]https://www.who.int/influenza/human_animal_interface/en/.
While Hong Kong has taken steps to tackle the avian influenza in the Special Administrative Region’s wet markets, multiple different subtypes of avian influenza (H1N1, H2N9, H3N2, H3N3, H3N6, and H4N6) continue to circulate in live-poultry markets in mainland China^[4]https://www.sciencedirect.com/science/article/pii/S0140673603153299.

The mortality rate of bird flu is estimated to be 60% making it at least ten times more lethal than COVID-19.