Bacteria vs. Virus

What's the Difference?

Bacteria are tiny, one-celled living organisms that can only be seen with a microscope. They live and breed in warm, moist environments in the body and elsewhere, growing quickly and causing infection. Bacterial infections can usually be treated with an antibiotic.

Viruses are smaller than bacteria and cannot be seen with a microscope. They grow inside the body and produce toxins (poisons) that can cause rashes, aches, and fevers. Viruses cannot be killed with antibiotics.

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