what is virus

A virus is a small infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat called a capsid. Viruses cannot replicate alone; instead, they must infect cells and use components of the host cell to make copies of themselves. They are unique because they are only alive and able to multiply inside the cells of other living things. Viruses are capable of latching onto host cells and getting inside them. Once inside, the virus uses the host cell’s machinery to replicate its own genetic material. Often, a virus ends up killing the host cell in the process, causing damage to the host organism. Viruses can infect humans, plants, animals, bacteria, and fungi. Some well-known examples of viruses causing human disease include AIDS, COVID-19, measles, and smallpox.