ANALYSIS - The AH7N9 avian influenza outbreak that affected humans
this year in China continues to worry the scientific community, as
evidenced by the continuous publication of studies on the outbreak,
writes Chris Wright, Senior Editor, for the Poultry Site.
At
the same time, the Chinese poultry sector is still having trouble and
continues to recover from the crisis caused by avian influenza. The
Chinese government just announced that it is giving the industry 300
million yuan (48.5 million dollars) more to help the poultry industry in
its recovery. This is added to the 900 million yuan that has already
been given to the industry. Aside from the central government subsidies,
ten provinces have established preferential policies to support the
poultry industry.
The latest figures from the China Animal Agriculture Association show
that the industry has recorded more than 40 billion yuan in losses
since the H7N9 outbreak in March. The losses resulted from the culling
of poultry that the government ordered and also due to the lack of
confidence in the poultry industry by consumers.
Commercial poultry, particularly chickens, was blamed for the
outbreak, although the actual source of the outbreak remains unknown.
What is clear is that in poultry the H7N9 virus was of low pathogenicity
and never mutated to be a highly pathogenic virus.
The unusual aspects of this new virus are, in fact, what so worries
the scientific community. That is the reason why almost on a weekly
basis, a new study is published about this outbreak which resulted in
133 people becoming ill, with 38 of those infected dying.
What is clear so far is that there was no sustained human to human
transmission of the virus, with the primary cause being that the people
affected had some sort of contact with live poultry (although this was
never confirmed one hundred per cent).
The P Word
The scientific community which works with influenza viruses is always
looking for those viruses with the potential to cause a pandemic, and
this new H7N9 virus seems to have that potential. The assumption about
pandemic viruses is that they will be a new virus mutation that can be
easily transmitted to humans, and because they are new, humans will not
have developed resistance to them.
The ongoing research has been of three basic types: virus
characterization, who was infected (and why) and how this virus affects
animals.
The research to see how the respiratory tract is affected has been
done with ferrets and mice. Ferrets are used because they have a very
sensitive respiratory tract.
A Japanese study found that the Chinese H7N9 virus caused more
mortality in mice than in ferrets and was more capable of replicating in
the lungs of mice in comparison to the other avian and human influenza
viruses studied. The H7N9 virus easily infected mice, which is not the
case with human influenza viruses, unless there is prior host
adaptation.
A study published in Nature by CDC (US Centers for Disease
Control) researchers found that the H7N9 viruses are capable of causing
infection in a direct contact animal model, but the viruses would need
to undergo additional adaptation to spread more easily by droplets or
through the air.
The most important finding of the CDC study, as well as other
studies, is that person to person transmission, especially through
respiratory droplet transmission, through coughs or sneezes, is a
necessary precondition for the virus to become capable of causing a
pandemic. Therefore, as of now, the Chinese H7N9 influenza virus
presents no “clear and present” pandemic danger, just a great deal of
concern
source
source
0 comments:
Post a Comment