What's the difference between a virus and bacteria?

The primary differences between bacteria and viruses come down to their complexity, how they live, and how they are treated.

Bacteria

• Nature: Bacteria are single-celled, living organisms. They are complex enough to survive on their own in diverse environments—from soil and water to inside the human body.
• Reproduction: They reproduce independently by dividing (binary fission).
• Treatment: Bacterial infections are treated with antibiotics, which work by killing the bacteria or stopping them from multiplying.
• Impact: While many bacteria are harmless or even helpful (like those in our gut), some cause infections such as strep throat, tuberculosis, or urinary tract infections.

Viruses

• Nature: Viruses are much smaller and are not considered fully "alive." They consist simply of a piece of genetic material (DNA or RNA) encased in protein. They cannot survive or reproduce without a host.
• Reproduction: They act as "hijackers." A virus invades a living cell and forces that cell to copy the virus’s genetic material, eventually bursting the cell to release new viruses to infect others.
• Treatment: Antibiotics have no effect on viruses. Viral infections are managed with vaccines (to prevent them) or antivirals (which may slow them down), though often the body's own immune system must fight the virus off.
• Impact: Viruses cause illnesses like the common cold, the flu, COVID-19, and chickenpox.

In short: Bacteria are living, independent cells that can be killed by antibiotics, whereas viruses are small genetic parasites that require a host cell to function and are not affected by antibiotics.