It would be reaaaally great if you could send a sample to Mcafee AVERT Labs or Mcafee Labs is what they call it. Anyway, this is their team who are responsible for making DATs being released by Mcafee and they will also be responsible for analyzing "suspicious" files.
If you were able to provide the sample virus to AVERT then they will give you a special DAT specifically for you called EXTRA.dat so you could immediately use this to clean your undetected viruses and NOT wait for tomorrow's released DAT. Anyway, the signatures applied in the extra.dat will always be released on the DATs released on the next day or two. So other people with Mcafee infected with YOUR undetected virus will be detected and cleaned as well.
To submit a file to AVERT you must ZIP the file and password protect it and set the password to INFECTED otherwise, they will just ignore your submitted file.
You could go to AVERT thru here: https://www.webimmune.net/