H7N7 More danger from bird flu

Not only H7N9 viruses pose a significant risk, H7N7 also pose a massive risk

08/22/2013

The spread of bird flu in China is increasingly worrying researchers worldwide. Since March, more than 130 people have been with the „novel H7N9 influenza A virus“ infected, 44 patients have died as a result of the infection, Chinese researchers describe together with British and US colleagues in the journal „Nature“ the past history of the epidemic. The research team headed by Huachen Zhu and Yi Guan from the University of Hong Kong has recently investigated the genesis of the H7N9 virus and discovered a link to the H7N7 virus.

Now the scientists fear that the avian influenza virus of the genus H7N7 could possibly be dangerous for humans. „Although there is no evidence to date that the H7N7 strain can infect humans“, but has been found in the current studies, „that the H7 avian influenza viruses are constantly mixing and increasingly exchanging genetic material“, report Guan and colleagues. The process is considered in the professional world as „reassortment“ indicates and holds the risk that H7N7 viruses could also develop into human-pathogenic viruses in the future.

Bird flu viruses swap genetic material
To the emergence of the H7N9 virus in China, the researchers said that the virus „is a reassortment of H7, N9 and H9N2 avian influenza viruses.“ This carries some amino acids, with which it could dock on the receptors of mammals. The scientists could show according to own data, „H7 viruses were usually first transferred from domestic ducks to chicken populations“ and then a reassortment with viruses of the genus H9N2 followed, resulting in the H7N9 virus emerged. Also, they discovered a hitherto unrelated H7N7 line. The H7N7 viruses have been detected in chickens and would have been shown to be infectious in further experiments in mammals, write Guan and colleagues. The discovery suggests, „that H7 viruses pose a threat that goes well beyond the current outbreak“, explain the researchers. The high prevalence of H7 viruses in poultry could lead to the generation of highly pathogenic variants, with a persistent risk that the viruses acquire a human-to-human transmissibility, so the conclusion of the international research team.

H7N7 bird flu viruses a previously unknown danger?
„H7 is out there in China and not just in the form H7N9“, co-author Richard Webby, influenza specialist at the St. Jude Children's Research Hospital in Memphis (Tennessee). Although the discovered H7N7 strain has not infected a human, researchers have found that the viruses can infect ferrets in laboratory tests, „which suggests that a transfer to humans is possible“, explained Yi Guan. In the experiments all ferrets would have developed severe pneumonia. Severe pneumonia was also one of the common bird flu symptoms with current H7N9 infections in China. Guan and colleagues conclude that a further spread of H7N7 virus in the chickens population could be expected to spread to humans in the medium term. Yi Guan therefore advocated better monitoring of the Chinese bird population.

Poultry markets as hotbeds of new bird flu variants
The research team led by Yi Guan had taken throat and intestinal smears from 1,341 birds, including chickens, ducks, geese, pigeons, partridges and quails, on poultry markets around Shanghai. Also, 1,006 water and faeces samples from bird markets were analyzed. „Over ten percent of the samples tested were positive for an influenza virus, of which 15 percent was for a H7 virus“, the researchers write. David Morens, influenza specialist at the US National Institutes of Health in Bethesda, Maryland explained, „that the evolutionary path followed by the viruses suggests that more surveillance and better hygiene practices in poultry markets are critical to monitoring the risks to human health.“ (Fp)

Also read about bird flu:
Avian influenza virus H7N9 in stool
Worrying experiments with bird flu viruses

Picture credits: schemmi