Spirit attachments can indeed take advantage of a weakened state of being to gain entrance, and then go to work on their host to worsen things for them, and this can include perturbing the emotions and the mental balance, potentially, if a person is vulnerable to such manipulations. There are also physiological changes and derangements that can be caused by the virus itself getting into the brain. This will have a physical component that can produce symptoms by disrupting brain function physiologically, and that can interfere with the possibility of consciousness and render a person catatonic. There are also perturbations that will trigger old karma, things that are stored in cellular memory, referenced through the akashic records, and can recapitulate in the current life and mimic a prior dilemma, such as being in a coma state.
Illness is always real because it is always an energetic perturbation, whether a product of the mind or a microbe, but there are many forms and causes still not appreciated by medicine because the science is simply not yet known. Most illness has a karmic origin and there is no medical awareness of or appreciation for the karmic mimicry the body can produce in creating symptoms that may be vague and undiagnosable, or a dead ringer for a common medical disorder that will result in a routine diagnosis and consequential medical treatment. Occasionally, that has some benefits if it is able to obtain symptomatic relief, but it will not heal the karmic dilemma, and if there are side effects and hazards from the treatment being invasive, which is usually the case, there may be a more negative outcome than if the person were simply left alone. This is a learning curve that eventually the medical establishment will come to grips with, but that is a long ways from today, unfortunately.