The practitioner points out in his suggested prayer enhancement, the general definition of scourges: “A source of widespread dreadful affliction and devastation such as that caused by pestilence or war. A means of inflicting severe suffering, vengeance, or punishment.” Would this prayer confer greater benefits, assuming people hold the broad intention conveyed by the definition of scourges?

This is precisely our point, that we are doubtful the majority of people will hold that definition in mind in all of its potential coverage categorically but will view it through a narrower lens, because you have specifically mentioned a virus, will be inclined to think in narrow terms about other viral infections or perhaps microbes in general. So while you can pray for anything you wish, if you expect this will be embraced and used with the full potential by the public, you will likely not see this happen to anywhere close to a full extent in outcome.