#13,596
While new, reassortant, influenza viruses can emerge practically anywhere, there are admittedly regions of the world where conditions are more conducive than others (see 2013's EID Journal: Predicting Hotspots for Influenza Virus Reassortment).
Places where:
- swine, poultry or other susceptible livestock population densities are high
- different types of farm animals are raised in close quarters
- there is a high degree of contact between farm animals and humans
- live bird markets are common
But they are far from alone.H10N8 infected 3 people and killed two in China over the winter of 2013-14, last spring we saw the first known human infection with H7N4, swine EAH1N1 has been cited as having one of the highest pandemic potentials in China, and their avian H4N6 viruses have recently been described as gaining worrisome mammalian adaptations.
China's recent success in (at least temporarily) quashing their H7N9 epidemic through the nationwide deployment of a new H5+H7 poultry vaccine - while a welcome development - doesn't preclude other subtypes from coming to to the fore.Of particular concern are the H6 avian viruses, which are ubiquitous in Asian poultry, and have recently:
- Jumped species (see EID Journal: Influenza A(H6N1) In Dogs, Taiwan)
- Caused at least one human pneumonia case in Taiwan (2013)
- Appear to have asymptomatically infected others (see EID Journal: Seropositivity For H6 Influenza Viruses In China),
- And which show signs of moving slowly towards mammalian adaptation Study: Adaptation Of H6N1 From Avian To Human Receptor-Binding.
Transbound Emerg Dis. 2018 Oct 9. doi: 10.1111/tbed.13037.
Continued reassortment of avian H6 influenza viruses from Southern China, 2014-2016.
Li J1, Quan C2,3, Xie Y4, Ke C5, Nie Y6, Chen Q7, Hu T1, Chen J7, Wong G8,9, Wang Q3, Feng L10, Yu H10, Liu Y8, Liu W2, Gao GF2,3,8,10, Liu WJ3, Shi W1, Bi Y2,8.
Abstract
H6 subtype avian influenza virus (AIV) was prevalent in poultry and could sporadically infect humans. Here, a total of 196 novel H6 AIVs isolated from poultry in eight provinces of China from 2014 to 2016 were phylogenetically characterized.
Our analysis revealed that they could be divided into two clades in the Asian H6 HA lineage, A/wild duck/Shantou/2853/2003(H6N2) (ST2853-like) (85.7%) and A/duck/Shantou/339/2000(H6N2) (ST339-like) (14.3%), in which ST2853-like strains predominate. These novel strains belonged to the H6N6 (n=165, 84.2%), H6N2 (n=30, 15.3%) and H6N3 (n=1, 0.51%) subtypes, which could be classified into 36 genotypes including 12 novel genotypes described in this study.
In particular, several strains possessed the V190 and S228 mutations in HA (H3 numbering), which is critical for human receptor binding and identical to the human-derived strain A/Taiwan/2/2013(H6N1). Furthermore, 10.3% of the H6N6 isolates possessed the N6-∆11b (59-69) deletion.
In summary, we describe phylogenetic and molecular characterizations of H6 AIVs in southern China and highlight the constant prevalence of H6 AIVs in poultry as well as adaptation to mammalian hosts. This article is protected by copyright. All rights reserved.
This pairing of the V190 and S228 HA mutations is something we've looked at before (see PLoS One: Structural and Functional Studies of Influenza Virus A/H6 Hemagglutinin).
They are of concern because they allow an avian flu virus to bind to either avian a2,3 receptor cells or to a2,6 human-like receptors, suggesting that they represent a growing threat to human health.Recent history suggests that as one influenza threat recedes, others come forward to take their place. The recent suppression of H7N9 in China - while a considerable victory - may prove only a temporary reprieve, as there are no lack of viral contenders in the wings.
All reasons why pandemic preparedness remains as vital as ever, even if the H7N9 threat seems reduced for now.
