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Study
fingers chickens, quail in spread of H7N9 influenza virus
Study
fingers chickens, quail in spread of H7N9 influenza virus
Date:
March 18,
2014
Source:
American Society for Microbiology
Summary:
Among the copious species of poultry in China, quail
and chickens are the likely sources of infection of H7N9 influenza virus to
humans, according to a paper. The H7N9 avian influenza virus was first reported
in humans in March 2013 in China. Since then over 375 human cases have been
confirmed and over 100 have died. Only 1 case has been reported outside of
China: A woman from Guangdong Province who was traveling in Malaysia and is
presumed to have contracted the virus in China. According to the World Health
Organization, most known human infections have resulted from direct or indirect
contact with poultry.
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Among the
copious species of poultry in China, quail and chickens are the likely sources
of infection of H7N9 influenza virus to humans, according to a paper published
ahead of print in the Journal
of Virology.
"Knowing
the likely poultry species lets us target our interventions better to prevent
human infections," says corresponding author David Suarez, of the United
States Department of Agriculture.
The H7N9
avian influenza virus was first reported in humans in March 2013 in China.
Since then over 375 human cases have been confirmed and over 100 have died.
Only 1 case has been reported outside of China: A woman from Guangdong Province
who was traveling in Malaysia and is presumed to have contracted the virus in
China. According to the World Health Organization, most known human infections
have resulted from direct or indirect contact with poultry.
Suarez'
laboratory originally became concerned about H7N9 after sequences from several
isolates were made available in public databases, early in the outbreak.
"We quickly recognized that the virus from this outbreak was unusual, and
represented a real human and veterinary risk," he says. Most of the genes
had come from a poultry virus that had existed in china for many years, and two
genes probably came from a wild bird isolate, he says.
"We
felt a major knowledge gap in the outbreak was that we didn't know which
poultry species was maintaining the virus and exposing people," says
Suarez. "With this information, better decisions can be made to control
and hopefully eradicate the virus."
In the
study, Suarez and his collaborators first infected seven species of poultry
with a human isolate of the Chinese H7N9 virus. The virus replicated well in
quail and chickens, and the former quickly infected their cage-mates, says
Suarez.
The virus
replicated less well in other poultry species, and did not transmit
efficiently. Pigeons were notably resistant to becoming infected. In additional
experiments, quail transmitted virus efficiently, while pekin ducks and pigeons
did not.
None of the
poultry species became sick when infected with H7N9, making detection of the
virus that much more difficult in the birds, says Suarez. "This work
supports the need for better surveillance in animal species for avian
influenza," says Suarez.
"The
silent carriage also creates a conflict between poultry producers, who want to
preserve their flocks, versus the public health goals of eradicating the
virus," says Suarez.
"This
work supports the field epidemiology studies that had identified live poultry
markets as the likely source of the outbreak," says Suarez. "The
Chinese correctly closed the live bird markets where they had human infections,
and that reduced the number of cases for a while. However, their efforts did
not eradicate the virus and it has returned for a second wave."
Story
Source:
The above
story is based on materials provided by American Society for Microbiology. Note:
Materials may be edited for content and length.
Journal
Reference:
- M. J. Pantin-Jackwood, P. J. Miller, E. Spackman, D. E. Swayne, L. Susta, M. Costa-Hurtado, D. L. Suarez. Role of poultry in spread of novel H7N9 influenza virus in China. Journal of Virology, 2014; DOI: 10.1128/JVI.03689-13