Viruses can infect all forms of life and are found anywhere there are cells, including in soil, water, and air. Viruses lie dormant until entering a host cell, usually through the nose, mouth or breaks in the skin. Once inside a host cell, the virus attaches and releases its genetic material, hijacking the cell's enzymes to produce new virus particles which then break free and infect other cells. Viruses are considered by some scientists to be both living and non-living, as they are inactive particles outside of a host cell but become active reproducers inside a living cell.