There are around 5,000 viruses identified. However, a virus can turn (mutate) its genetic material generating new viruses or more resistant viruses than its predecessors. This means that every virus spreads or reproduces in the presence of a cell that it has invaded, so the isolated virus cannot reproduce and may even die.
Some viruses affect a single species, while others manage to affect several. The severity (degree of mortality) of the virus will be related depending on the cure (found or not) of the virus. Thus, there are viruses that cannot be considered deadly today, such as the mumps virus, while others with no apparent cure, are considered deadly, such as HIV (AIDS virus).
On the other hand, it is important to clarify that each organism fights the virus by which its cells have been infected. The state of the immune system of the affected living being will fight this virus. The better the state of the immune system, the more tools you will have to fight (with antibodies) the virus. These antibodies are found in the blood and are called lymphocytes.
- See also: Bacteria.