Check clamav version
To find the calmav version run the following command
#clamscan –version
ClamAV 0.93.3/8683/Wed Nov 26 12:28:25 2008
To upgrade the calmav form source, uninstall the previous version and reinstall the new source.
To upgrade from rpm package, user rpm -Uvh
rpm -Uvh clamav-db-0.xx.rpm
rpm -Uvh clamav-devel-0.xx.rpm
rpm -Uvh clamav-0.xx.rpm
rpm -Uvh clamd-0.xx.rpm