Viral DNA is the genetic material found in certain viruses, which are tiny infectious agents. Unlike bacteria, viruses cannot reproduce on their own; they need a host cell to replicate. The viral DNA carries the instructions for making new virus particles and can integrate into the host's DNA, affecting the host's cellular functions. When a virus infects a host, it injects its viral DNA into the host cell. This DNA then hijacks the cell's machinery to produce more viruses. Some viruses, like HIV and herpes, can remain dormant in the host's cells, leading to chronic infections.