Hey, I've had the same problem, on both of my machines, i am trying to gather my notes to help you.
I eventually fixed it.. it was a pain. :/
until i can replicate the fix again, here is my uname -sr:
Linux 3.10.0-693.17.1.el7.x86_64
it involved editing the /etc/clamd.conf file about 4 different places, as far as i know.
one major one was the DirectoryData was /var/clamd i think i changed it to /var/LIB/clamd
and another of hand that i remember was the username, was clamav, i believe i changed that to reflect "clamupdate"
as the "clamav" was NOT in my /etc/passwd list..
...eventually.. i got it working, i will post what i can step-by step, IF i can figure it out again.
Cheers