A 41-year-old man from eastern China could be the world’s first human infection of the H10N3 strain of bird flu, according to the country’s health agency, adding that the risk of transmission was low.
The National Health Commission said on Tuesday that the man from Jiangsu province had various symptoms including fever and was hospitalised at the end of April.
Genetic analysis confirmed the virus strain on Friday and emergency contact tracing did not find other cases or abnormalities, the commission said.
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“Experts think the analysis of the virus’ complete genome showed the H10N3 strain had an animal origin and had not adapted to infecting humans effectively yet,” it said.
“This infection is an accidental animal-to-human cross-species transmission. The risk of a large-scale transmission is very low.”
The commission said there were no previously reported human H10N3 infections, making the Jiangsu man possibly the world’s first documented case of this strain.
The patient’s condition had stabilised and he was ready to be discharged from hospital, it said.
Gregory Gray, an infectious disease epidemiologist from Duke University, said H10N3 was an unusual influenza A virus to be found infecting a human.
“It will be interesting to see what genetic changes permitted it to infect a human,” Gray said.
“However, I am not surprised. The more we look for novel viruses as a cause of illness among patients the more we are likely to find them. Novel influenza A viruses are perhaps the easiest to find as we have good clinical diagnostics to detect all of these viruses in healthcare settings.”
Benjamin Cowling, a professor of epidemiology and biostatistics at the University of Hong Kong, said it was always a concern to hear about human infections with avian influenza viruses.
“It reminds us of the threat posed by zoonotic infections,” Cowling said, referring to a disease that jumps from an animal to a human.
“Hopefully this particular case is just a sporadic case and we won’t hear about any more infections with H10N3.”
Leading Chinese scientists such as Gao Fu, director of the Chinese Centre for Disease Control and Prevention, have called for more surveillance of influenza because other strains have been found in at least 46 countries, including H5N8, which infected seven Russian farm workers late last year.
The first documented incident of an avian influenza virus jumping species to infect humans was the 1997 outbreak of H5N1 in Hong Kong, in which 18 people were sickened and six died.
Bird and swine flu are both caused by the influenza A virus, the only type of flu virus that can lead to a pandemic. Influenza is classified based on two surface proteins and 18 HA subtypes and 11 NA subtypes have been discovered.
The H10 subgroup of influenza A was first isolated from a chicken in Germany in 1949, and the first human infection, of the H10N7 strain, was reported in Egypt in 2004, according to a 2018 paper on the H10 subgroup written by Robert Webster from St Jude Children’s Research Hospital in the United States and colleagues.
China has seen several human infections of another strain, H10N8.
In 2013, a 73-year-old woman with chronic illnesses from Nanchang in the southern province of Jiangxi was hospitalised with a fever and died nine days later, according to a 2014 paper by Shu Yuelong and other National Health Commission researchers.
She was discovered to have been infected by the H10N8 strain. The woman had visited a live poultry four days before she got sick, the paper said.
Two other H10N8 human cases were reported in 2014 in the same province, according to a report by Hong Kong’s Centre for Health Protection.
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