Virus are all the time mutating. The reason mutations are a problem with virus is because (A) there are so many and (B) they reproduce so quickly.
It’s estimated that there are 10 to the 31 virus in the world. That’s:
10 million trillion trillion
This is far more than all the stars in the universe.
Even though the chance of a mutation in any particular reproduction is very, very small, because of the enormous number of virus and their very short reproductive cycle, mutations regularly happen.
Virus are microscopic. But, because there are so many, if they were laid end to end, they would stretch 100 million light years. In one gram of dental plaque, there are more virus than all humans who ever lived. In your gut, there’s a pound of virus. Over the course of a year, you evacuate more than your body weight of virus.
Obviously, we are fighting virus all the time. Almost always we win. But, sometimes, we lose. Actually, since virus are parasites, they don’t really want us to lose. They want us to get sick, but not die. But, sometimes things get out of control.
Good sanitation and habits of cleanliness are really important to keep things under control. Historically and still in many countries, poor sanitation is a contributor to viral and other contagious diseases, with consequences including listlessness and stunted physical and mental development.
When there were few of us, and we were dispersed over a wide area, sanitation and cleanliness wasn’t so important. But, being increasingly an urban species, sanitation and cleanliness are, today, absolutely necessary.
As to whether virus are a form of life is controversial. They have genetic materials and reproduce, but only with the assistance of a host cell. Host cells range from bacteria to the cells of advanced plants and animals. The virus hack into the host cell, and cause the host cell to reproduce more virus of the same kind.
When the host cell is exhausted, a multitude of virus attacks other cells of the host life form, or migrate to other like life forms. The transmission from one to another life form can happen when coughing or with the aid, for example, of an insect.
Living as we do with virus within us and all around us, our bodies have both generic and specific defenses against virus. As we grow from infancy to adulthood, we usually develop more defenses. But, when young or debilitated by sickness or old age, our immune systems are weakened and we are vulnerable.
Vaccines, once developed, can be helpful; but, can be costly and may have side-effects. In any case, they won’t be immediately available.
Historically, times of the introduction of new contagious disease combined with harsh winters, crop failures, and other conditions weakening an entire population, were times of devastation. During the Bubonic Plague or Black Death, perhaps half of the population of Europe succumbed to contagious disease.
Through the early years of the Republic, our cities suffered recurrent outbreaks of yellow fever. Cholera, always a problem, periodically rose to epidemic proportions. The Spanish Flu, following World War I, infected a quarter of the world’s population, and claimed the lives of perhaps 4 percent.
A few years ago, it was ebola. Today, the coronavirus. Tomorrow, because of mutation, it will be something else.