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Urgent search for flu source
Researchers suspect H7N9 virus is in bird markets as human cases rise rapidly.
Declan Butler
09 April 2013
...Chinese health authorities say that they have 400 laboratories looking for genetic changes in the virus.
?We are going to be sitting with bated breath over the next month to find out what happens,? says Michael Osterholm, who heads the University of Minnesota?s Center for Infectious Disease Research and Policy in Minneapolis....So many cases in such a short time over such a wide area ? up from three cases in two cities a week ago ? is ?a very concerning situation?, says Osterholm.
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Researchers know that H7 flu viruses mainly infect wild birds such as ducks, geese, waders and gulls, and that they occasionally jump into poultry flocks. Kwok-Yung Yuen, an infectious-disease expert at the University of Hong Kong, notes the proximity of the reported human cases to the Yangtze river delta, home to many wild birds, and to Chongming Island near Shanghai, a renowned site for watching migratory birds. ?It?s likely wild ducks and geese that are carrying it,? he suggests.
But this H7N9 virus has not yet been detected in wild birds in the area...
...
Wherever the virus originated, a crucial question is whether it could become established in poultry, creating a reservoir that might lead to continued, sporadic human infections.
...
...It would be next to impossible to detect H7N9 through routine surveillance for sick poultry among China?s 6 billion domestic birds. ?This means stopping animal-to-human transmission is impossible,? says Masato Tashiro, a virologist at the Influenza Virus Research Center in Tokyo, the World Health Organization?s influenza reference and research centre in Japan.
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Because flu viruses evolve rapidly, comparing viral sequences from each of the human cases might reveal whether person-to-person transmission is occurring, says Andrew Rambaut, an expert in the evolution of human viral pathogens at the University of Edinburgh, UK. If many patients have very similar viral sequences, then that would imply human spread; if viral sequences are more diverse, it would imply that each person had separately picked up infections from birds. Only four sequences from four human cases are so far available, but virologists are sequencing more and posting them on the GSAID flu database.
If human-to-human transmission does start to occur, ?further spread may be inevitable?, warns Tashiro. Humanity has never been widely exposed to H7 or N9 flu viruses, and so lacks resistance to these subtypes. If a pandemic were to occur, it would probably have a severe toll....
Full text:
Urgent search for flu source
Researchers suspect H7N9 virus is in bird markets as human cases rise rapidly.
Declan Butler
09 April 2013
...Chinese health authorities say that they have 400 laboratories looking for genetic changes in the virus.
?We are going to be sitting with bated breath over the next month to find out what happens,? says Michael Osterholm, who heads the University of Minnesota?s Center for Infectious Disease Research and Policy in Minneapolis....So many cases in such a short time over such a wide area ? up from three cases in two cities a week ago ? is ?a very concerning situation?, says Osterholm.
...
Researchers know that H7 flu viruses mainly infect wild birds such as ducks, geese, waders and gulls, and that they occasionally jump into poultry flocks. Kwok-Yung Yuen, an infectious-disease expert at the University of Hong Kong, notes the proximity of the reported human cases to the Yangtze river delta, home to many wild birds, and to Chongming Island near Shanghai, a renowned site for watching migratory birds. ?It?s likely wild ducks and geese that are carrying it,? he suggests.
But this H7N9 virus has not yet been detected in wild birds in the area...
...
Wherever the virus originated, a crucial question is whether it could become established in poultry, creating a reservoir that might lead to continued, sporadic human infections.
...
...It would be next to impossible to detect H7N9 through routine surveillance for sick poultry among China?s 6 billion domestic birds. ?This means stopping animal-to-human transmission is impossible,? says Masato Tashiro, a virologist at the Influenza Virus Research Center in Tokyo, the World Health Organization?s influenza reference and research centre in Japan.
...
Because flu viruses evolve rapidly, comparing viral sequences from each of the human cases might reveal whether person-to-person transmission is occurring, says Andrew Rambaut, an expert in the evolution of human viral pathogens at the University of Edinburgh, UK. If many patients have very similar viral sequences, then that would imply human spread; if viral sequences are more diverse, it would imply that each person had separately picked up infections from birds. Only four sequences from four human cases are so far available, but virologists are sequencing more and posting them on the GSAID flu database.
If human-to-human transmission does start to occur, ?further spread may be inevitable?, warns Tashiro. Humanity has never been widely exposed to H7 or N9 flu viruses, and so lacks resistance to these subtypes. If a pandemic were to occur, it would probably have a severe toll....
Full text:
