Virus

A virus is a tiny infectious agent much smaller than bacteria, consisting of genetic material (DNA or RNA) encased in a protein coat. It cannot reproduce on its own; instead, it enters a host cell and hijacks its machinery to produce more virus particles. These new viruses then infect additional cells, causing illness. Viruses can cause a wide range of diseases, from the common cold to more severe conditions like influenza or COVID-19. Because they rely on host cells to multiply, viruses are classified as biological agents capable of propagating quickly within a host organism.