Use a comma between coordinate modifiers. Modifiersare coordinate if they modify the same word. You can test to see if the modifiersare coordinate by inserting and between them. If the description stillmakes sense, then the modifiers are coordinate.
Ebola viruses are known as filoviruses for their long, filamentlikeappearance under a microscope.[Long and filamentlikemodify the appearance of the virus equally, so a comma is needed between them.]
--"Research Notes," Science News
The McGraw-Hill Companies, Inc..