Can I disable these virus database notifications?
Yes, with the LICENSE_WARNING= site configuration variable (please see here for details). Please be aware this also turns off most LISTSERV license warnings, including warnings that inform you that your maintenance is about to expire, or that your product LAK is about to expire. It is L-Soft's strong recommendation that license warnings not be disabled under any circumstances, and then only with the understanding that you do so at your own risk.