Like the flu virus, viruses and bacteria mutate all of the time and medical research labs have to keep adjusting/developing the vaccines, antibiotics according. Hundreds of all strains of virus usually develop over time, like the flu. Some years it kills hundreds of thousands and some years under a hundred thousand. Each usually dies out in time as we develop, slow or fast to that particular strain, immunity and/or effective drug and/or vaccine are created. Still, this virus seems relatively ineffective on healthy people and at its worst its death rate still under 33%, even over age 85, which most patients have more than vital health-risk they are managing, if nothing more than inactivity.
Even lethal viral mutations change, weaken, mix with others as they evolve and become ineffective against the host's immunity or drugs/vaccines kill them or render them much less effective, such as HIV, which began as a certain death virus in its initial forms.
__________________  Jeanie and Tibbe One must do the best one can. You may get some marks for a very imperfect answer: you will certainly get none for leaving the question alone. C. S. Lewis |