There is only a notifcation or an allert on the clients, when the virus signatures are out of date.
But we had very often the problem, that the SEPM didn't downloaded the new virus signatures without restart of the services or server.
This happened with version 14.x nearly every 2-4 weeks.
What happens: New virus signatures are available at the Symantec servers and shown in SEPM, but they are never downloaded. Or just the situation that the SEPM losses the connection to the internet.
There is no warning that the virus signatures n the server are older than 24h or 48h. In the past the signatures changed once a day at least.
So allow an email to be sent, if the signatures on the server are getting older than x hours/days!
Running computers with outdated virus signatures when there are updates available are a real high security risk!