Scientist examining plaque test, 2019

Scientist examining plaque test, 2019

In this 2019 photo, a Centers for Disease Control and Prevention (CDC) scientist was examining the results of a plaque assay, which is a test that allows scientists to count how many flu virus particles (virions) are in a mixture. To perform the test, scientists must first grow host cells that attach to the bottom of the plate, and then add viruses to each well, so that the attached cells may be infected. After staining the uninfected cells purple, the scientist will then count the clear spots on the plate, each representing a single virus particle.

CDC Public Health Image Library, Image 23213