Photo Credit – FAO
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From The Lancet this morning, a fast track study by Chinese researchers, a commentary by Marion Koopmans, Menno D de Jong from the Netherlands, and a podcast interview with Prof Kwok-Yung Yuen MD that points an accusatory finger at poultry in the transmission of the H7N9 virus to humans.
H7N9 transmission from poultry
Poultry has been suspected as the source of human H7N9 transmission in China, where there have been over 100 cases and 20 deaths. In a fast-track Article, Chinese investigators obtained samples from live poultry markets suspected of being linked to human cases of H7N9 influenza. By comparing the viruses found in poultry with those found in human cases, investigators were able to confirm the infected poultry as the source of human H7N9 transmission. The findings have implications for how the outbreak should be controlled, and are discussed in a Comment and podcast.
Human infections with the emerging avian influenza A H7N9 virus from wet market poultry: clinical analysis and characterisation of viral genome
Yu Chen MD, Weifeng Liang MD, Shigui Yang PhD, Nanping Wu PhD, Hainv Gao MD, Jifang Sheng MD, Hangping Yao PhD, Jianer Wo PhD, Qiang Fang MD, Dawei Cui PhD, Yongcheng Li MD, Xing Yao MD, Yuntao Zhang MD, Haibo Wu PhD, Shufa Zheng PhD, Hongyan Diao PhD, Shichang Xia MD, Yanjun Zhang PhD, Kwok-Hung Chan PhD, Hoi-Wah Tsoi MPhil, Jade Lee-Lee Teng PhD, Wenjun Song PhD, Pui Wang PhD, Siu-Ying Lau MPhil, Min Zheng MPhil, Jasper Fuk-Woo Chan, Kelvin Kai-Wang To, Honglin Chen PhD, Prof Lanjuan Li MD, Prof Kwok-Yung Yuen MD
Summary
Background
Human infection with avian influenza A H7N9 virus emerged in eastern China in February, 2013, and has been associated with exposure to poultry. We report the clinical and microbiological features of patients infected with influenza A H7N9 virus and compare genomic features of the human virus with those of the virus in market poultry in Zhejiang, China.
Interpretation
Cross species poultry-to-person transmission of this new reassortant H7N9 virus is associated with severe pneumonia and multiorgan dysfunction in human beings. Monitoring of the viral evolution and further study of disease pathogenesis will improve disease management, epidemic control, and pandemic preparedness.
This study is based on a small number of hospitalized patients (n=4) with established contact with poultry 3-8 days prior to developing severe pneumonia and H7N9 infection.
Researchers reported `The genes of the H7N9 virus in patient 3's isolate were phylogenetically clustered with those of the epidemiologically linked wet market chicken H7N9 isolate.’
The researchers conclude,`These findings suggest sporadic poultry-to-person transmission.’
This study also highlights the clinical picture of infection in these cases (2 of whom died).
The presumed incubation period ranged from 3 to 8 days (mean 5·8 days). Mean age was 56 years (table 1). None of the patients were obese and none had upper-respiratory-tract symptoms or conjunctivitis.
All patients had fever, and lower-respiratory-tract symptoms (including dyspnoea, cough, and sputum), and one had prominent myalgia (table 1).
Chest radiography and CT of all patients showed multilobar patchy consolidation and diffuse alveolar opacities (figure 1A—1F). CT of patients 1 and 4 showed ground glass changes in some areas. Mean time between onset of symptoms and respiratory failure was 9 days.
The Podcast with Dr. Kwok-Yung Yuen, which runs about 10 minutes, is quite informative. You’ll find more perspective in the accompanying comment Avian influenza A H7N9 in Zhejiang, China.
As this report from NBC’s Maggie Fox indicates, if this outbreak is purely transmitted by poultry - and no other reservoir of the virus is found - then this outbreak might be brought under control by slaughtering poultry and disinfecting markets.
Poultry markets likely source of new bird flu in China
By Maggie Fox, Senior Writer, NBC News
Poultry markets where birds are sold live and slaughtered on the spot are the likely source of the new H7N9 bird flu that’s killed more than 20 people in China, researchers said Thursday.
Genetic analysis shows the strain that infected some of the first patients is very similar to a strain found in chickens and pigeons at so-called “wet” markets, the team of Chinese researchers said. Their report was rushed into publication by the Lancet medical journal.
