What's the Difference Between Bacteria and Viruses?

Many infectious diseases are caused by either bacteria or viruses, two types of germs that are both invisible to the naked eye. On closer inspection, it turns out bacteria and viruses are actually quite different! Bacteria are single-celled, living organisms that can exist and perform life functions on their own. By contrast, viruses are not living creatures. Instead, they’re made up of genetic material enclosed within a protein shell called a capsid. The two germs are also drastically different in size. An average-sized bacterium is about 2 micrometers, or 2 millionths of a meter, in length. Viruses are considerably smaller. Most fall between 0.02 and 0.4 micrometer in length, too small to be seen with normal microscopes! As living creatures, bacteria can reproduce on their own, typically through binary fission. For viruses to replicate, they must hijack a living cell and force it to produce new copies of virus. Once viruses multiply, they leave the host cell and spread to infect other cells, sometimes throughout the rest of the body. On the other hand, bacterial infections are usually confined to a single area of the body in what is known as a localized infection. Treatment will differ depending on whether an infection is viral or bacterial in nature. Tetanus, tuberculosis, strep throat, and other diseases caused by bacterial infections are treated with antibiotics. These medications aren’t effective against viruses. Instead, diseases caused by viral infections, such as influenza, measles, and COVID-19, are treated with antiviral medications. Knowing the difference between bacteria and viruses isn’t just a technical distinction—it can save lives!