Viruses (Science Foundations)

No one knows the origins of viruses. They have been on Earth for so long that it is believed that they may predate the first living cells. Today, viruses are found around the world, infecting bacteria and the cells of plants, fungi, animals, and humans. Viruses are parasites that cannot copy themselves and must invade other forms of life to reproduce. As they invade, viruses can inflict fatal diseases and transform normal cells into tumor cells. In Viruses, examine the life cycles of these tiny parasites, the ways they affect their hosts, and the ways that their ability to mutate present an ongoing challenge to the medical community.