TEM of an ultra-thin specimen revealed some of the ultrastructural morphologic features seen in 1918 influenza virus virions. The prominent surface projections on the virions are composed of either the hemagglutinin, or neuraminidase type of glycoproteins. Composed of what looked like dots or tubules, was a dense envelope known as a capsid, which surrounded each virion's nucleic acid constituents. The flu is a contagious respiratory illness caused by influenza viruses. It can cause mild to severe illness, and at times can lead to death. Magnification unknown.