This is a very simple way to hook up clamdscan to watch one or more
directories for new files, and then run the scanner on them. It will use
zenity to report scanning outcome in a dialog.
sudo apt-get install zenity clamdscan
./clamnot ${HOME}/Downloads […] &
Simple debug output is written to stdout/stderr; better logging (including a full copy of each scan result) is written to the journal.