Christian Zuniga, PhD
Viruses are very, very small. Although their existence was suspected since the 19th century, they were too small to be seen . Viruses are so small that taking a picture with an ordinary light microscope would not detect them. Figure 1 shows an image of a MERS Coronavirus taken with an electron microscope . The diameter of the virus is on the order of 100 nm (or 0.0000001 m). For comparison, the width of a human hair is around 80 um so a virus is around 8000 times smaller.