How to find & remove virus from site

There seems to be a virus on my client’s site and not sure how to find & remove it. Here are details from my client:

We’ve been told recently by a number of users of our website that there is a virus that attempts to download from our site. Consequently, our site is blocked by some outside users (e.g., Verizon employees), other users can get to it but get a virus as they click through. HostMySite has been contacted twice about this, and they claim to have run scans both times and have come up empty in terms of being to identify a virus or cause. They suggested that we check other possible sources.

Website: https://www.avalonecon.com/

Any ideas on how to find & remove? thanks!