The influenza virion is enveloped and expresses two surface proteinsthat are essential to virulence: hemagglutinin (HA) and neuraminidase (NA). _______________ is essential for entrance into the respiratory epithelium and _______________ cuts through sialic acid and essential for release of the newly synthesized virions. Health Science Science Nursing NURS 5350 Share QuestionEmailCopy link Comments (0)