Commentary
Transmission Concerns for High Path H7 In England
Recombinomics Commentary 16:07
June 4, 2008
As at least 50 percent of the people exposed to infected poultry had H7 antibodies detectable with the modified assay, it was estimated that avian influenza A/H7N7 virus infection occurred in at least 1000, and perhaps as many as 2000 people. The seroprevalence of H7 antibodies in people without contact with infected poultry, but with close household contact to an infected poultry worker, was 59 percent. This suggests that the population at risk for avian influenza was not limited to those with direct contact to infected poultry, and that person-to-person transmission may have occurred on a large scale
From February 18 to June 1, 2004, a total of 77 symptomatic persons were reported to the British Columbia Centre for Disease Control. Fifty-seven had suspected (n = 55) or confirmed (n = 2) avian influenza infections.
An outbreak of the H7 strain of bird flu at a farm in central England is "highly pathogenic", officials said on Wednesday.
All the chickens on the farm have been slaughtered following detection of the virus, which does not pose a high risk to humans, at the farm in Banbury, Oxfordshire late on Tuesday.
The above comments describe high path H7 outbreaks. The H7N7 outbreak in The Netherlands was PCR confirmed in 89 cullers, but H7 antibodies were in more than 1000 contacts. The H7N3 outbreak the following year was linked to 2 confirmed cases but 55 suspected cases. The current case has been confirmed to be high path H7, but details have not been released other than the standard propaganda statement on a lack of human risk or transmission.
This myth is regularly stated by DEFRA and then distributed by the popular press. It has no scientific basis and is support by an insensitive or fatally flawed assay and limited testing.
Recent experiments have demonstrated increase affinity for human receptors, adding additional evidence for the efficient H7 transmission to mammals, including humans. The detection of H7 is poor. The current outbreaks in England and the United States were likely due to wild birds, yet neither surveillance systems detected H7 in wild birds. In the US, the surveillance also failed to detect the H7N3 virus in the birds that developed antibodies.
The outbreak in the United States is assumed to be low path because the infected flocks did not have evidence of disease. However, the low path H7N2 outbreak in England a year ago was also linked to many patients with symptoms. Four of these patients were confirmed, but others had a relatively severe course and were hospitalized, although none were linked to pneumonia and/or death.
Although most of the H7 bird outbreaks have associated confirmed cases, the low sensitivity of the assays raises questions about the extent of spread in humans.
The positive examples above clearly demonstrate that humans are easily infected with H7, and the outbreaks last year clearly show that such infections need not be high path H7.
Media Links
Recombinomics Presentations
Recombinomics Publications
Recombinomics Paper at Nature Precedings