Virus Facts
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Viruses are simpler than bacteria, made up of genetic code (DNA or RNA) with a protein shell – some scientists do not describe them as being alive. Viruses can be 20 to 250 nanometers in size. Viruses can’t reproduce on their own, they need to take over another cell such as plants, animals or humans. Some viruses are useful. Viruses called bacteriophages, kill bacteria and are used to protect people against harmful bacteria in food.