Saturday, 1 February 2014

Neither market nor farm poultry all that positive for H7N9; songbirds the culprit...?

Following on from yesterday's post, "If not poultry then what?", I thought it worth noting the impressive numbers from the Chinese Ministry of Agriculture.

From 2013:

  • 1,630,000 poultry and environmental samples tested
    • 88 POS; all from live bird markets
    • None from poultry farms
From 2014, to date:
  • 33,400 poultry and environmental samples
    • 8 H7N9 POS; all from live bird markets
    • None from poultry farms
The other alternative to answer the question in my heading; the testing methods are at fault. 

No detail of what approach has been used to obtain these numbers in the links below. Viral culture and serology with some PCR have been noted before. I'd wager culture yields chicken scratchings compared to PCR for detecting virus in he wild; but serology has successfully been a pillar upon which animal testing rests. So that's why the numbers above are such a quandary for the epidemiologist who reads about the high frequency of links between human disease and exposure to poultry.

It would be nice to see some technical papers on antibody test testing (development and validation) at some point. If only to reassure everyone that the testing methods are doing what testing methods should be doing.

See #3 below for influenza PCR discussion at WHO.

Sources..