安装 CLAMAV 并尝试扫描后，我看到此错误。我该如何解决这个问题？
$ clamscan scan
LibClamAV Error: cli_loaddbdir(): No supported database files found in /var/lib/clamav
ERROR: Can't open file or directory
----------- SCAN SUMMARY -----------
Known viruses: 0
Engine version: 0.98.7
Scanned directories: 0
Scanned files: 0
Infected files: 0
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 0.003 sec (0 m 0 s)