Virus particles can be rod shaped, like TMV on the left or isometric (spherical) as on the right.
Teresa Sawyer, Electron Microscope Facility. Images taken with the Titan ChemiStem made by FEI CO in Hillsboro OR.
Submicroscopic, infectious agent, too small to be seen with a compound microscope, that multiplies only in living cells. A virus consists of nucleic acid (DNA or RNA) surrounded by a protein coat.