# 7188
Although this study was actually published several days ago – and bits and pieces have surfaced in recent news stories - the steady barrage of breaking news has prevented me from posting it until now. From the Chinese Science Bulletin we get a genetic analysis of H7N9 samples pulled from live poultry markets in Shanghai.
Teams led by Professor Chen Hualan (National Avian Influenza Reference Laboratory in Harbin) collected 970 test samples from drinking water, feces, contaminated soil, and cloacal and tracheal swabs from birds in live markets in Shanghai and Anhui province.
Of these 970 samples, 20 were positive for the H7N9 avian flu virus; 10 from chickens, 3 from pigeons, and 7 were from environmental samples. Furthermore, all of the positive samples were collected in Shanghai.
Analysis showed these H7N9 viruses to be a reassortant, with six internal genes lifted from the H9N2 avian virus, while the source of the H7 (HA) and N9 (NA) were not completely clear.
The found the HA genes were most closely related to a duck H7N3, while the NA shared the highest homology with H4N9 or H11N9 influenzas from ducks.
The H7N9 Reassortment – Credit Eurosurveillance
Some of their other findings match what we’ve seen in other studies (see Eurosurveillance: Genetic Analysis Of Novel H7N9 Virus), such as finding the amino acid leucine at position 226 of the HA, a change that is typically found in human flu viruses, and is viewed as a sign of partial adaptation from avian to mammalian hosts.
All of the poultry samples tested contained the 627E residue in their PB2 protein – while the first three human samples sequenced carried the E627K substitution; the swapping out of the amino acid Glutamic acid (E) at position 627 for Lysine (K).
Glutamic acid (E) at this position is a hallmark of avian influenza viruses, and is believed to make the virus better adapted to replicate at the higher temperatures commonly found in birds (41C).
Human flu viruses normally have Lysine (K) at position 627. That mutation supposedly makes the virus better adapted to replicate at the lower temperatures (roughly 33C) normally found in the upper human respiratory tract.
The authors write that this change `may have significantly contributed to their pathogenicity and lethality in humans.’
Follow the link below to read the study in its entirety, and for a quick synopsis, you’ll find a press release here.
Isolation and characterization of H7N9 viruses from live poultry markets—Implication of the source of current H7N9 infection in humans
JianZhong Shi, GuoHua Deng, PeiHong Liu, JinPing Zhou, LiZheng Guan, WenHui Li, XuYong Li, Jing Guo, GuoJun Wang, Jun Fan, JinLiang Wang, YuanYuan Li, YongPing Jiang, LiLing Liu, GuoBin Tian, ChengJun Li, HuaLan Chen
Abstract
On March 31, 2013, the National Health and Family Planning Commission announced that human infections with a previously undescribed influenza A (H7N9) virus had occurred in Shanghai and Anhui Province, China.
To investigate the possible origins of the H7N9 viruses causing these human infections, we collected 970 samples, including drinking water, soil, and cloacal and tracheal swabs of poultry from live poultry markets and poultry farms in Shanghai and Anhui Province.
Twenty samples were positive for the H7N9 influenza virus. Notably, all 20 viruses were isolated from samples collected from live poultry markets in Shanghai.
Phylogenetic analyses showed that the six internal genes of these novel human H7N9 viruses were derived from avian H9N2 viruses, but the ancestor of their HA and NA genes is uncertain. When we examined the phylogenetic relationship between the H7N9 isolates from live poultry markets and the viruses that caused the human infections, we found that they shared high homology across all eight gene segments. We thus identified the direct avian origin of the H7N9 influenza viruses that caused the human infections.
Importantly, we observed that the H7N9 viruses isolated from humans had acquired critical mutations that made them more “human-like”. It is therefore imperative to take strong measures to control the spread of H7N9 viruses in birds and humans to prevent further threats to human health.
The authors conclude by writing:
The novel features that the new H7N9 viruses possess, including: previously unidentified HA and NA composition; wide prevalence in avian hosts and the environment; an exceptional adaptive ability in humans; and the potential to acquire multiple basic amino acids at the HA cleavage site and evolve into a highly pathogenic form, are a major cause for concern with respect to public health worldwide.
Forceful measures, such as continued surveillance in avian and human hosts, control of animal movement, shutdown of live poultry markets and culling of poultry in affected areas must be taken during this initial stage of virus prevalence to
prevent a possible pandemic.It is also imperative to evaluate the pathogenicity and transmissibility of these H7N9 viruses, and to develop effective vaccines and antiviral drugs to combat them and reduce, if not eliminate, their threat to human health.
