Viruses are usually classified into two types, one called DNA viruses and one called RNA viruses. DNA viruses have a DNA structure that is a double helix of genetic material called deoxyribonucleic acid, and RNA viruses are single-stranded ribonucleic acid called RNA. These two viruses are characterized by the need to be parasitic in cells in order to replicate and proliferate. Because viruses exist inside cells, they are very tricky to treat. If you kill the virus inside the cell, it is possible to kill the cell as well. Therefore, the usual approach to intracellular viruses is to inhibit replication and proliferation. The usual approach for isolated viruses is to kill the virus, such as using disinfectants, alcohol can kill the isolated cells or isolated viruses directly. For intracellular viruses, it is usually possible to suppress the virus by inhibiting its reproduction and proliferation. Content source: Dr. You Lai