Virology tidbits

Virology tidbits

Wednesday, 5 February 2014

Emerging Influenza Viruses

Frequently media outlets are reporting the identification of a novel strain of Influenza and in recents years this includes the identification of novel strains of avian influenza. More often than not, novel strains are identified because they have shown to cause severe disease in humans infected. 
Following the conformation of a human case of Influenza A H7N9 in January of this year -and subsequent culling of chicken in Hongkong and a ban of poultry exports-, the Financial Times reported the identification of a "novel" Influenza virus, A/ H10N8 in a 73 years old female patient. The corresponding case study was published on February 5th 2014 in The Lancet and emphasizes that the virus isolated from this patient is genetically distinct from previous isolates from avian sources, thus potentially adapted to infect humans - so strictly speaking it is a virus which is already established in avian species and after crossing into the human population mutated to cause disease. Mind the words here - adapted to infect humans, which implies that so far human to human transmission has not been proven to occur. In fact, H10N8 is one of many avian Influenza viruses which have been shown the ability to infect humans. Some of them have been shown to be able to be transmitted between humans and thus have the potential to cause a worldwide pandemic. So far however this has not occurred and it may be that some of the potential viruses might have become attenuated during human to human transmission and/or that cross-immunity caused by circulating viruses might be sufficient to prevent disease. Indeed it is known that relatives from patients infected and hospitalized for "bird flu" are often seropositive for antibodies - whether they acquired the virus from the patient or from the environment is not entirely clear, but there are indications that they were infected by the same sources as the patient. 

I was delighted to read in the Financial Times that they interviewed a well known virologist and expert on Influenza from the Imperial College London, Wendy Barclay, who pointed out that we have to careful in the interpretation of the results. The caveat was indeed correctly stated in the Lancet article but might have been overlooked by less through investigation. 
Reading a well researched article in the press on a topic which can easily cause widespread fear in my opinion justifies why we should pay for newspapers instead turning to free news sites who are dependent on advertisers for funding. 

Further reading:

Clinical and epidemiological characteristics of a fatal case of avian influenza A H10N8 virus infection: a descriptive study
To KK, Chan JF, Chen H, Li L, & Yuen KY (2013). The emergence of influenza A H7N9 in human beings 16 years after influenza A H5N1: a tale of two cities. The Lancet infectious diseases, 13 (9), 809-21 PMID: 23969217

HaiYing Chen, Hui Yuan, Rongbao Gao, Jinxiang Zhang, Dayan Wang PhD, Ying Xiong, GuoYin Fan, Fan Yang, Xiaodan Li, Jianfang Zhou Shumei Zou, Lei Yang, Tao Chen, Libo Don (2014). Clinical and epidemiological characteristics of a fatal case of avian influenza A H10N8 virus infection: a descriptive study The Lancet DOI: 0.1016/S0140-6736(14)60111-2

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