Researchers have isolated a novel reassortant avian influenza A H10N8 virus from a patient in China who died on December 7, 2013. The patient lived in Nanchang City, Jiangxi Province, and became ill on November 27, 4 days after visiting a live poultry market. Genetic analysis suggests the new variant may spread among humans.
HaiYing Chen, MD, from Nanchang City Disease Control and Prevention in China, and colleagues describe the case in an article published online February 5 in the Lancet.
"A genetic analysis of the H10N8 virus shows a virus that is distinct from previously reported H10N8 viruses having evolved some genetic characteristics that may allow it to replicate efficiently in humans. Notably, H9N2 virus provided the internal genes not only for the H10N8 virus, but also for H7N9 and H5N1 viruses," author Yuelong Shu, PhD, from the Chinese Center for Disease Control and Prevention, Beijing, explained in a journal news release.
The female patient, aged 73 years, became ill on November 27 (day 0), developed a fever on day 2, and was admitted to the hospital on day 4. A chest computed tomography scan on day 4 revealed consolidation of the right lung lower lobe and increased density of the left lung lower lobe.
The patient's condition deteriorated rapidly, and she was admitted to the intensive care unit on day 5. A chest radiograph on day 6 found bilateral pleural effusions, which rapidly progressed to ground-glass opacities and consolidation on day 8.
She was given antibiotics from day 3 through day 8, and glucocorticoids days 5 through 7. Antiviral therapy ( Tamiflu, Genentech USA) was begun on day 6. She developed severe pneumonia, septic shock, and multiple organ failure and died on December 6 (day 9).
Tracheal aspirate specimens obtained on days 7 and 9 were positive for avian influenza A H10N8 virus and negative for seasonal influenza viruses (H1, H3 or B), H5N1, H7N9, and H9N2. Sputum and blood cultures and deep sequencing analysis found no coinfection with bacteria or fungi.
Sequence analyses of the A/Jiangxi-Donghu/346/2013(H10N8) (JX346) virus found that all 6 internal genes were closely related to the H9N2 viruses that are currently circulating in poultry in China.
The hemagglutinin cleavage site contains a single basic amino acid, arginine, which indicates low pathogenicity in poultry.
The JX346 virus was sensitive to the neuraminidase inhibitors oseltamivir and zanamivir.
A total of 17 close contacts were identified (11 healthcare providers, 5 family members, and 1 carer); none had any signs of influenza-like illness in the 2 weeks after contact with the patient.
"The H10 and H8 gene segments might have derived from different wild bird influenza viruses reassorted to give rise to a hypothetical H10N8 virus in wild birds, which infected poultry and then reassorted with H9N2 viruses in poultry to give rise to the novel reassortant JX346 (H10N8) virus," the authors write.
A mixture of glutamic acid and lysine at residue 627 in the PB2 protein was identified in the original tracheal aspirate samples. This mutation is thought to be associated with increased virulence and adaptation in mammals.
This virus was not found at the poultry market. The H10N8 virus has been isolated twice before, once from a water sample obtained from China's Dongting Lake in Hunan Province in 2007 and once at a live poultry market in Guangdong province in 2012. No human infection with an N8 subtype has ever been reported.
The authors warn that the pandemic potential of this virus should not be underestimated. "A second case of H10N8 was identified in Jiangxi Province, China on January 26, 2014. 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," coauthor Mingbin Liu, MD, from Nanchang City Center for Disease Control and Prevention, concluded in the news release.
source: www.medscape.net
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