We have many automatic and natural defense systems for dealing with viruses, bacteria, fungi, and other foreign bodies. It is generally believed that viruses are different from bacteria in that bacteria operate outside
cell walls while viruses choose a host cell in order to replicate themselves.
Some can mutate — for instance, HIV dodges the immune memory system in order to survive. With all viruses there can be the added problem of secondary bacterial infection. Although modern drugs can
deal with fungal or bacterial infections, they used to be unable to invade viruses or to penetrate the walls of cells inhabited by viruses. However, some are now able to overcome certain viruses’ sophisticated defense
systems. This development could lead to the production of entire families of antiviral drugs in the future, which could have a similar outcome to the story of modern antibiotics (see below). Should an antibiotic be given to a
person with a virus, and should it enter the cell wall, aggressive side effects can take place; these may include severe nausea, dizziness, immune system imbalance, and emotional swings