OM ("OfficeMacro") is a family name for all Microsoft Office Macro viruses. These are viruses which infect not only one Office application but several - for example, Word and Excel.
For example, if you're looking for the description of "O97M/Jerk", "OfficeMacro.Jerk" or "Macro.Office.Jerk" virus, see the description of "Jerk".
Allow F-Secure Anti-Virus to disinfect the relevant files.
For more general information on disinfection, please see Removal Instructions.