Viruses: What they are and how they spread

Viruses are smaller than the microscope can see. They are infectious agents that replicate only inside the living cells of an organism. Organisms are classified as multicellular animals, plants, fungi, and unicellular microorganisms such as bacteria. Humans are multicellular animals. Viruses are not considered to be living organisms, but their existence is dependent on infecting living organisms, entering their cells and forcing the cells to produce thousands of copies of itself. This is how they replicate. The more they replicate, the greater the chance mutations will occur that will make the...