Link to Pubmed [PMID] – 24112132
Influenza Other Respir Viruses 2014 Jan;8(1):123-30
Influenza A viruses have an envelope made of a lipid bilayer and two surface glycoproteins, the hemagglutinin and the neuraminidase. The structure of the virus is directly dependent on the genetic makeup of the viral genome except the glycosylation moieties and the composition of the lipid bilayer. They both depend on the host cell and are in direct contact with the environment, such as air or water. Virus survival is important for virus transmission from contaminated waters in the case of wild aquatic birds or from contaminated surface or air for humans.
http://www.ncbi.nlm.nih.gov/pubmed/24112132