Avian influenza (Bird flu): GB surveys of wild bird populations to screen for the presence of avian influenza - summary of results (2006/2007)
Background information: GB surveys of wild bird populations to screen for the presence of Avian Influenza.
Samples taken from wild birds are initially tested by the Polymerase Chain Reaction (PCR) laboratory test; this detects genetic material (RNA) specific to all influenza A viruses including those from avian species. This is a very sensitive screening test. If this test gives a positive result, the samples are subjected to further confirmatory tests to identify and characterise the virus. This involve attempts to grow (or culture) the virus; when this is successful the virus can usually be fully characterised.
Sometimes it is only possible to detect parts of the virus, not an entire virus. In this case the virus may be incomplete (partially destroyed); these viruses are not viable. Laboratory results may therefore involve only partial identification of the virus i.e. detection of genetic material or the haemagglutinin (H) subtype only (and not the neuraminidase (N)). These further tests also involve determining whether the virus is a highly pathogenic avian influenza (HPAI) virus or a low pathogenic avian influenza (LPAI) virus, again this may not be possible if there is not enough viable virus present in the sample.
Positive results: A positive result is a laboratory result where there is at least correct identification of the virus by haemagglutinin (H) subtype. Results that are only positive by M gene screening test are not reported as positive on the web site.
Only final positive laboratory results will be reported on the web page, that is when the complete suite of laboratory tests has been completed on the sample(s).
Summary of results 2006 from August onwards
The summary is described in terms of numbers of birds tested at VLA Weybridge (the EU reference laboratory for avian influenza). Birds targeted for surveillance are gulls, waders, ducks, geese and swans. The date of a positive result refers to the date that the sample was taken.
Birds arriving in Great Britain from northerly latitudes as part of the autumn migration generally start to arrive from August onwards. Therefore information published on this web page applies to the period from August 2006 onwards, this coincides with the start of the targeted surveillance strategy.
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12 June, 2008