What is living that a virus or parasite used for resources and shelter?

Living organisms, such as plants, animals, and humans, provide viruses and parasites with the necessary resources and shelter to survive and reproduce. These pathogens exploit their hosts by utilizing their nutrients and cellular machinery to replicate and thrive, often at the host's expense. While viruses require a host cell for replication, parasites can live on or within their hosts, leading to various degrees of harm. This relationship highlights the complex interactions within ecosystems, where one organism's survival can significantly impact another's well-being.