Viruses are everywhere cellular life is present, often in unfathomable numbers. They mutate very often, frequently by recombining with other viruses. This means that new viruses are constantly being generated.
Viruses are specific for certain types of hosts, meaning that there are bacterial viruses, plant viruses, animal viruses, etc. Therefore, fortunately, not all viruses are able to infect human cells. Still, our body is constantly being exposed to and having to deal with new viruses. Most often, they are quickly eliminated by our immune system; they may even go by unnoticed. But as the COVID-19 pandemic has left abundantly clear, every now and then, a new virus can wreak havoc on our lives.
As we’ll learn in this article, viruses are very simple, but despite their simplicity, they are very effective and impressive little creatures. We’ll also learn how our immune system rises to the challenge.
WHAT IS A VIRUS?
Viruses are a unique group of infectious agents. Viruses aren’t microbes because they aren’t cells. And because they aren’t cells, they aren’t typical life forms or “organisms.” [Historically, definitions of life asserted that a living organism must be composed of one or more cells, but some modern criteria allow for non-cellular life forms, of which viruses are the prime example.]