It apparently ceased to exist sometime over the weekend.
Err http://ppa.launchpad.net trusty/main amd64 Packages
404 Not Found
STDERR: W: Failed to fetch http://ppa.launchpad.net/ubuntu-clamav/ppa/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
---- End output of apt-get update ----
It apparently ceased to exist sometime over the weekend.