H7N3 in Saskatchewan Canada
Recombinomics Commentary
September 27, 2007
Highly pathogenic H7N3 avian influenza has been detected in a commercial poultry operation in Saskatchewan, the Canadian Food Inspection Agency (CFIA) announced today.
H7N3 is not normally associated with serious human illness.
The above comments from the press release from the Canadian Food Inspection Agency confirm HPAI H7N3 in Canada. The comment on human illness has two qualifiers, which have been dropped from media reports. H7N3 is easily transmitted from birds to humans as well as human-to-human. However, most infections are mild and assays for H7 genetic information in healthy host (birds or people) is abysmal, Antibody testing of convalescent sera is more sensitivity and reliable. The serological tests provide conclusive evidence for efficient transmission.
The last major outbreak of H7 in birds in Canada was the 2004 outbreak in British Columbia. The H7N3 initially tested as low path, but HPAI was detected within days, and the outbreak led to culling of millions of birds. Two workers were confirmed H7N3 infected, but many more had symptoms, which include conjunctivitis.
The most recent H7 infection was in England in late May. The low path H7N2 was linked to multiple confirmed cases, and many more suspect cases. Although an update on human testing of suspect cases was promeised at the Options VI presentation in Toronto, the update has not been made public.
H7 infections are cause concern because the virus is efficiently transmitted to mammals. The only reported bird flu fatality that was not H5N1 was a death linked to the 2003 H7N7 outbreak in the Netherlands. Serological testing of cullers and contacts indicated well over 1000 people had H7 antibodies.
Although the current outbreak is almost certainly linked to wild birds, the influenza surveillance program in Canada failed to detect high or low path H7 in wild birds this year or last year.
Sequence information on the poultry outbreak would be useful.
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