More Bird Flu Surveillance Failures in Western Europe
Recombinomics Commentary
May 26, 2007
The outbreak in Wales involves Rhode Island Red chickens that the farmers bought 2 weeks ago, the British Broadcasting Corporation (BBC) reported today. The birds began dying the day after they arrived at the farm, and by May 17, 10 of 15 had died.
Christianne Glossop, chief veterinary officer for Wales, told the BBC that authorities don't believe the disease is spreading rapidly.
The above comments signal yet another avian influenza surveillance failure in England. Since H7 is a reportable disease and no recent H7N2 outbreaks on farms have been reported, it is likely that the current outbreak is linked to migratory birds that infected the birds several weeks ago.
Like the H7N3 outbreak last year in England, there was no detection of H7 in wild birds prior to the outbreaks on farms. Similarly, the program in England had failed to detect H5N1 in live wild birds. H5N1 was detected in a swan that washed up on the shores of Scotland last year, but no H5N1 infected birds were detected by the surveillance program in England.
Similarly, last year H5N1 was detected throughout western Europe in February and March, and similar sub-strains of the Qinghai H5N1 were found in Germany, Austria, Italy, Slovenia, and the Czech Republic which were virtually identical to the H5N1 in a healthy teal in the Nile Delta in December, 2005. The sequence of the H5N1 in Egypt strongly suggests that H5N1 was present throughout western Europe in the fall of 2005, yet went undetected. No H5N1 was reported in western Europe or Africa until early 2006.
This season, H5N1 in Egypt had M230I, encoded by sequences that match H7N3 in England, or H5N1 in northern Germany. All patients with M230I in Qinghai H5N1 died. M230I is also found in all season flu strains (H3N2, H1N1, and influenza B), which may contribute to the efficient spread of H7N2 in England. Four patients have already tested positive for H7N2, including one without poultry contacts. The status of the vendor that sold the infected birds, as well as contacts, is unclear.
Thus far, the symptoms of the four known positives are mild, and three suspect cases have already been discharged from the hospital. However, H7 can recombine with H5N1 or other H7 isolates. To date there has been one fatality reported with H7N7. The sequence of H7 from the 2003 fatal case was more genetically complex than the H7 from the bird isolates raising the possibility of dual infections in the veterinarian, leading to a more virulent strain.
The levels of H5N1 and H7 in the area remain unclear because of surveillance programs that lack the sensitivity to detect H5N1 in live wild birds. There may be similar problems detecting H7 since neither the H7N3 nor H7N2 outbreaks were signaled by the wild bird surveillance program.
These detection failures remain causes of concern.
Media sources
Recombinomics Presentations