Describe what makes a virus or bacterium a pathogen.

A pathogen is an organism or agent that causes disease in another organism. Both viruses and bacteria can be pathogens. 1. Viruses: Viruses are pathogens because they can infect host cells and hijack their cellular machinery to replicate, often damaging or killing the host cell in the process. Viruses cannot replicate on their own and must infect a host cell to propagate. 2. Bacteria: Bacteria become pathogenic when they produce virulence factors, such as toxins or enzymes, that damage tissues, evade the immune system, or cause inflammation. Pathogenic bacteria can infect tissues, survive within the host, and often multiply, causing disease.