I am using Norton AV.. Previously I could run a LiveUpdate and have the most current virus definitions. But now according to Symantec, Liveupdate is done once a week unless there is something urgent that would require it done immediately. Their website shows their definitions library at 58980 yet the last LiveUpdate was done on February 27 with total of 58847 (check the Symantec site) SO my definitions library is short by 133.
If I run a LiveUpdate manually, I am told that I am current yet their site says different...

The following is a clip from their "Am I Protected" page...

Total Viruses Detected: 58980

LiveUpdate:
Virus Definitions released February 27
Norton AntiVirus Corp. Edition Defs Version: 40227e
Norton AntiVirus Corp. Edition Sequence Number: 15084
Total Viruses Detected: 58847