Microscopic view of H7N9
A report that will appear in the October 2013 issue of The American Journal of Pathology suggests that the emerging influenza virus H7N9 has pandemic potential.
First reported in March 2023 in China it was though to be spread from infected poultry,and that human to human transmission was unlikely.
Research has found however that the virus attaches to the epithelium in both the upper and the lower respiratory tract. Usually the lower respiratory tract is infected which makes human to human transmission less likely. It’s the discovery of upper respiratory tract colonization that has worried the scientists. Virulence is increased in conditions where both the upper and lower respiratory tract are infected.
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. “These characteristics fit with increased virulence of these emerging avian H7 viruses compared to that of human influenza viruses,” says Dr. Kuiken.
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. “However, the fact that the emerging H7N9 virus has caused infection mainly in individual human cases suggests that it has not acquired all the necessary properties for efficient transmission among humans,” notes Dr. Kuiken.(source)