The H7N9 subtype of avian influenza A virus was for the first time found to infect humans
since the outbreaks in March 2013 in China. Concerns about its risk on human
public health rises, and the mechanisms of pathogenesis and host immunity are studied.
The ultra-structure of H7N9 virus infections is characterized, and reported in this issue.
Viruses were grown in Madin-Darby canine kidney (MDCK) cells and human lung explants
tissues, and morphogenesis features of viral replication were examined by electron
microscopy. The cover depicts virus particles budding/releasing in alveolar space
and an induced sieve-like structure in the cytoplasm.