An ecosystem consists of all interactions within in a given area, along with interactions between their physical environment.

I would say that an ecosystem consists of all interactions within a community of organisms in a given area, along with interactions between their physical environment. It is however difficult to define the spatial boundaries of an ecosystem, and the definition is simplified somewhat to allow for a conceptual understanding. Consider for example how migrant birds may enter a particular region in Africa from Europe during the European winter. What is the spatial bounds of the ecosystem then, considering that they have imported energy sourced in Europe to Africa?

When a virus infects a host cell, it uses the cell's machinery to make copies of its own genetic material in a process called replication. finally, during the process of self-assembly, that protein shell and the copies of the virus's genetic material are assembled into new viruses.