[exim] String Search - What am I doing wrong?

I am trying to conduct a search (condition) in an ACL.

condition = ${if match {$spam_report:}{VIRUS}}

The above WORKS.

My understanding when using the match command the right element is
considered a REGEX, even though I don't need that functionality I don't see
any other way to conduct a contains search. I'm trying to look in the
$spam_report variable for the string VIRUS.

As mentioned, as written above works.

But I actually need to search for the string VIRUS(

Now that becomes a problem as ( is important in REGEX.

I tried escaping like this VIRUS\( and also VIRUS\\(

No luck with either of these, I will get an error like this:

failed to expand ACL string "${if match {$spam_report:}{VIRUS\(}}": regular
expression error in "VIRUS(": missing ) at offset 6

What am I doing wrong here? How do I escape the opening bracket?