No Evidence Nonsense on H7N2 Transmission in England
Recombinomics Commentary 22:44
February 11, 2008
The special blood tests - known as serology - were undertaken on 19 people who had symptoms at the time of the incident. Four of these - two in North Wales and two in North West England - were confirmed by laboratory testing at the time of the incident to have low pathogenic H7 avian flu associated with diseased poultry. The other 15 people had flu-like symptoms but had tested negative for the virus at that time.
There is no microbiological evidence of others being infected. However, there have only been a handful of H7 cases reported worldwide and laboratory testing of such very unusual strains is still developing.
HEALTH experts have said there is no evidence to suggest that a strain of avian flu found in North Wales last year had spread from person to person.
The above comments on the human to human transmission (H2H) of H7N2 in England in May, 2007 once again perpetuate the media myth on transmission of avian influenza to humans. The outbreak was unusual because there were more people with symptoms than birds. In May there is little seasonal influenza in England, so the symptoms in contacts left little doubt that H7N2 was being transmitted H2H. However, there were major technical issues associated with the detection of the virus itself, so follow-up serology testing was planned.
Investigators presented data at the Options VI “Breaking News” session in Toronto in June, promising results. Serology testing involves comparison of paired samples, one collected around the time of infection, and the second collected a month later during convalescence. Infections are associated with sero-conversion or a rising titer.
In the past, H7 infections in birds were associated withy infections in humans. The most dramatic examples of H2H were linked to the 2003 H7N7 outbreak in the Netherlands. An assay using horse erythrocytes indicated over 1000 contacts had H7 antibodies, demonstrating efficient H2H transmission.
The comments above clearly indicate there have been technical issues linked to the serological testing. It is eight months after the announcement in Toronto, and the media release has no real news. Clearly the serology is at best, incomplete, yet headlines of “no evidence” of H2H are presented. Since the evidence is not in, comments citing “no evidence” are meaningless.
This news follows the “no evidence” announcement on H5N1 in the mute swans in Dorset. The “no evidence” is meaningless, because the assays lack sensitivity for detecting H5N1 in healthy wild birds.
These press releases citing “no evidence” should cease. They are at best misleading, and neither H5N1 nor H7N2 read the press releases.
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