February 05, 2014
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China reports human infection with new avian influenza virus

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A human infection with new avian influenza A(H10N8) was confirmed in a woman from Nangchang City, China, who died of the infection, researchers reported in The Lancet.

A second case of the reassortant virus also was identified in an individual from Jiangxi Province on Jan. 26, the researchers said in a press release.

“A genetic analysis of the H10N8 virus shows a virus that is distinct from previously reported H10N8 viruses, having some genetic characteristics that may allow it to replicate efficiently in humans,” Yuelong Shu, PhD, of the Chinese Center for Disease Control and Prevention in Beijing, said in the press release. “Notably, H9N2 virus provided the internal genes not only for the H10N8 virus, but also for H7N9 and H5N1 viruses.”

The woman was a 73-year-old from Nanchang City in China. She presented to the hospital with fever and severe pneumonia on Nov. 30. She deteriorated rapidly, despite antibiotic and antiviral treatment, developed multiple organ failure and died 9 days after illness onset.  No information is available yet on the second case.

The researchers tested tracheal swabs from the patient, which were taken 7 days after illness onset, with reverse transcriptase polymerase chain reaction, viral culture and sequence analyses. They found that the virus was a new genetic reassortment avian-origin H10N8 virus. All of the genes were of avian origin, with six internal genes derived from avian H9N2 viruses known to circulate in poultry in China. The virus isolated is designated as A/Jiangxi-Donghu/346/2013(H10N8), or JX346.

“The results suggested that JX346 might originate from multiple reassortments between different avian influenza viruses,” Shu said. “The H10 and H8 gene segments might have derived from different wild bird influenza viruses reasserted to give rise to a hypothetical H10N8 virus in wild birds, which infected poultry and then reasserted with H9N2 viruses in poultry to give rise to the novel reassortant JX346 (H10N8) virus.”

According to the researchers, the virus had a mutation in the PB2 gene that is often associated with increased virulence and adaption in mammals, which could enable the virus to be more infectious to people.

The strain was previously isolated from a water sample from China’s Dongting Lake in Hunan province in 2007. It was also detected at a live poultry market in Guangdong province in 2012. However, there has never been human infection with an N8 subtype reported.

The woman had visited a live poultry market a few days prior to infection, the researchers said, suggesting that the incubation was 4 days, similar to other avian influenza viruses. But no H10N8 virus was found in samples from the poultry site. The source of the infection is unknown.

The researchers warned that this influenza virus has pandemic potential, especially since the second human infection was confirmed.

“This is of great concern because it reveals that the H10N8 virus has continued to circulate and may cause more human infections in the future,” Mingbin Liu, MD, from the Nanchang City Center for Disease Control and Prevention, said in the press release.