The Rubik's cube of influenza A genes spins up a new lineage of H7N7

Click to enlarge. A (very) summary view of the latest
contributing influenza viruses that precedes the emergence of
human infections with influenza A(H7N9) virus
in south-east China in 2013.

Lam and a global host of collaborators, writing in Nature on the 21st of August, have identified a previously unknown influenza A(H7N7) virus line circulating in chickens. The authors indicate that more influenza viruses lurk among poultry and that active surveillance is needed. This report comes from testing 1,341 pairs of oropharyngeal and cloacal swabs and 1,006 faecal and waters samples from live bird markets (LBMs) in Wenzhou and Rizhao of Zhejiang province, as well as Shenzhen from Guangdong province.


In a complex alphabet soup of influenza A virus findings, the authors, sequenced 34 H7N7, 4 H7N9 and 19 H9N2 egg-isolated viruses but also found H7N2 and H7N3 in ducks. Animals tested were chickens, ducks, geese, pigeons  partridges and quail.

The authors note that rather than wild birds from Europe and Korea, the neuraminidase (NA or N) gene segment from H7N9 is more temporally related to those from H11N9 and H2N9 found in wild birds (wild water fowl, Northern shoveller and common teal) in Hong Kong during 2010-11 with links to domestic ducks in China prior to the H7N9 outbreak this year. Overall, domestic ducks proved to be an important mixing pot between wild birds and chickens.

And it's not just H7N9; the H7N7 found in chickens reminds us that the colours on the cubes are many and are in constant motion. These virus may become/may already be enzootic (endemic in non-humans) and so continuing exposures to live poultry in markets and backyards remains a continuing source of risk for new zoonoses.

H7N9 antibody in Vietnam.

A study by MF Boni and colleagues describe the presence of either specific, or cross-reactive antibodies (which can arise after infection by a different influenza virus, but react with the H7N9 test) to the avian influenza A(H7N9) virus. These antibodies were detected in the sera of a cross-section of people from south Vietnam and were found at higher titres (levels) than antibodies to H5 but below those to H9 viruses. Human seasonal influenzavirus antibody levels were much higher than avian levels.
The protein array method used may not be comparable to haemagglutination inhibition (HI) or neutralization assay.
Results revealed a general increase in the amount of anti-haemagglutinin (HA) IgG antibody with age. This is fairly normal as our exposures to virus accumulate an immune "memory" over time.

There was no significant difference whether the samples came from rural or urban locales or from areas known to often keep chooks in the backyard, versus areas that do not.

The H7N7 and H7N9 avian influenza viruses differ by only ten amino acids in HA so it is likely IgG to H7N7 will cross-react with the H7N9.