The ClamAV package is not installed in the Bitnami AWS images by default
$ sudo apt list --installed | grep -i clamav
WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
The posts you mentioned talk about the antivirus software but they don't specifically say that it's installed by default. Our developers saw that the package was installed (the user can install it) and they mentioned that to the users.
I suggest you contact the ClamAV developers to know more about the error you found. You can also uninstall it if you want, that package is not required for the application to run.
That's the number of viruses the application knows about. It's not the number of viruses you have in the system.