The new study found that avian-origin H7N9 influenza A virus, which has recently emerged in humans, attaches moderately or abundantly to the epithelium of both the upper and lower respiratory tracts.
In the current study, using virus histochemical analysis, the investigators looked at the pattern of attachment of two genetically engineered emerging H7 viruses (containing the hemagglutinin (HA) of either influenza virus A/Shanghai/1/13 or A/Anhui/1/13) to fixed human respiratory tract tissues and compared the findings to attachment patterns seen with human influenza viruses with high transmissibility but low virulence (seasonal H3N2 and pandemic H1N1) and highly pathogenic avian influenza (HPAI) viruses with low transmissibility and high virulence (H5N1 and H7N7).
They found that like other avian influenza viruses, the H7N9 viruses attached more strongly to lower parts of the human respiratory tract than to upper parts. However, compared to other avian influenza viruses, the attachment to epithelial cells by H7N9 in the bronchioles and alveoli of the lung was more abundant and the viruses attached to a broader range of cell types.
A third notable finding was a more concentrated attachment of H7N9 viruses in ciliated cells of the nasal concha, trachea, and bronchi, suggesting the potential for efficient transmission among humans.
The study has been published in The American Journal of Pathology.