Does WSUS update anti-virus programs

You can if you like, but in reality sccm just manages a wsus service, so you'd be doing double the work. Chances are you can do the same things you're doing and perhaps more by using sccm.

Update

To elaborate, you can run two WSUS servers if you want, and install the sccm software update point role on one of them. As far as updates go, you can use group policy to point your machines to your non-sccm wsus server for updates. When the sccm client is installed on machines, and the software update mode is enabled, you can use sccm to deploy whatever updates you want at a time, be it just virus defs or what not.

However, this may not solve your problem, because as I said SCCM uses WSUS or update deployment, therefore some updates also will not install w/out a reboot first. SCCM will install whatever updates it can w/out a reboot, and IME virus defs fall into that category. And, just to reiterate, you will be managing two update servers now, although the newer version of sccm has automatic update deployment so technically that should make things easier for you.

See: http://moonlightsoft.blogspot.com/2016/08/error-0x80244019-occurred-while.html (let it translate) It worked for me! Appearantly the WSUS server has problems when the client needs to download big updates like 1609. After you add the Mime type, it works.