Meanwhile, scientists said that based on
information from genetic data and lab tests in China, the H7N9 virus
appears to infect some birds without triggering noticeable symptoms, AP
“We speculate that when this virus is maintained in poultry the disease
will not appear, and similar in pigs, if they are infected, so nobody
recognizes the infection in animals around them, then the transmission
from animal to human may occur,'' said Dr Masato Tashiro, director of
the World Health Organization's influenza research center in Tokyo and
one of the specialists who studied the genetic data. “In terms of this
phenomenon, it's more problematic.’’
This behavior is unlike the virulent H5N1 strain, which set off warnings
when it began ravaging poultry across Asia in 2003. H5N1 has since
killed 360 people worldwide.
“In that sense, if this continues to spread throughout China and beyond
China, it would be an even bigger problem than with H5N1 in some sense,
because with H5N1 you can see evidence of poultry dying, but here you
can see this would be more or less a silent virus in poultry species
that will occasionally infect humans,'' said University of Hong Kong
microbiologist Dr Malik Peiris, a Sri Lankan expert who also examined
the information. Dr Peiris is chair professor of the Virology School of
Public Health at HKU.
Dr Peiris praised Chinese health authorities for being forthcoming with
data and information, but said animal health agencies needed to step up
and act quickly. He urged China to widely test healthy birds in live
animal markets in the parts of the country where the human infections
have been reported to find out what bird species might be hosting the
virus and stop the spread.
“If you don't stamp it out earlier now, there won't be any chance of
stamping it out in the future,'' Dr Peiris said. “It already may be too
late, but this is the small window of opportunity that really one has to
grasp, as quickly as possible.''
Other information gleaned from the genetic data was that the H7N9 virus
was what scientists call a “gene re-assortant’’ _ in which three bird
viruses swapped genes among themselves _ undergoing changes that allowed
it to adapt more easily, though not fully, to human hosts, WHO's
Tashiro said. One change has allowed it to lodge onto the surfaces of
cells of mammals, making it easier to infect humans.
“The tentative assessment of this virus is that it may cause human
infection or epidemic. It is still not yet adapted to humans completely,
but important factors have already changed,'' Tashiro said.
In the wake of the outbreak, the Chinese Center for Disease Control and
Prevention shared the genetic sequence of the new virus with the global