There is an experiment that has been performed millions of times that could be useful here.
If what is known as a virus is really just cell fragments of a host body, then the DNA in those cell fragments should be identical to the DNA of the host body. Testing the DNA of the fragments, however, reveals that the fragment DNA is different from the host body, but identical to the DNA of the fragments of another COVID patient.
It happens that the DNA of cell fragments from people suffering from Covid around the world is more or less identical, with minor modifications. Conversely, healthy people generally do not show any such cell fragments at all.
Therefore, some sort of foreign entity is present in Covid patients. This entity is the Covid virus, but you can call it something else, if it makes you happy.