Recombinomics Commentary 19:59
June 3, 2008
The Chief Veterinary Officer, Nigel Gibbens, has today confirmed Avian Influenza in chickens on premises near Banbury in Oxfordshire after preliminary tests were positive for the H7 strain.
The Health Protection Agency has advised that it is important to remember that H7 avian flu remains largely a disease of birds. The virus does not transmit easily to humans, as evidenced by the small number of confirmed infections worldwide to date. Almost all human H7 infections documented so far have been associated with close contact with dead or dying poultry. The risk to human health posed by H7 avian influenza viruses remains low. Nonetheless, the local Health Protection Unit will be identifying and following up those who may have had contact with the infected poultry and provide guidance and advice, and preventative medication as appropriate.
The above comments from DEFRA describe another H7 outbreak in England. Once again there was no warning provided by the wild bird surveillance program. There was an H7N2 in England almost exactly one year ago, and an H7N3 outbreak almost exactly two years ago.
H7 infections are easily transmitted to humans, and once again the DEFRA words of assurance highlight a lack of confirmed cases, which is largely dependent on an insensitive assay that fails to detect H7 in symptomatic and hospitalized patients.
Last year there were almost as many suspect human cases as avian cases. The suspect cases are almost certainly linked to H7N2 infections, because there is little seasonal flu at this time of the year in England. Last year H7 infections in the owners of the index farm were not confirmed.
The data was presented a year ago in Toronto. At the time most of the suspect cases were not aln confirmed, and although results were promised at the meeting, little new data was released and the number of confirmed H7N2 cases remained at four.
H7 infections are efficiently transmitted to humans, In the 2003 H7N7 outbreak, antibodies were detected in more than 1000 contacts, base on H7 antibodies. Most of the patients had mild or eye disease. Last year the H7N2 cases were more severe and respiratory, but most of the suspect cases were not confirmed.
Media reports are descibing H7N3 antibodies in culled poultry in northwet Arkansas.
The recent results with A/New York./107/2003(H7N2) has increased concerns over human H7 infections, DEFRA press releases notwithstanding.
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