What are 3 major groups of viruses based on the organisms they infect?

1. Animal viruses infect animals, including humans. Examples include the influenza virus, the human immunodeficiency virus (HIV), and the measles virus.

2. Plant viruses infect plants. Examples include the tobacco mosaic virus, the potato virus Y, and the cucumber mosaic virus.

3. Bacterial viruses, also called bacteriophages, infect bacteria. Examples include the T4 bacteriophage, the λ bacteriophage, and the M13 bacteriophage.