How Does Natural Selection Impact the Proliferation of Superbugs?

How Does Natural Selection Impact the Proliferation of Superbugs?

Image Credit: Socha, Arek (artist). (2016). Virus Microscope Infection [digital art]. Retrieved from

If you follow current events, you’ve likely heard the term “superbug” before. You may have heard stories of superbugs causing terrible infections or even killing people because they won’t respond to medication.

Simply put, superbugs are a type of harmful microbe that can no longer by killed by the usual antimicrobial drugs; virus superbugs stop responding to anti-viral medications and bacteria superbugs stop responding to antibiotics. Sometimes superbugs stop responding only to certain kinds of antimicrobial drugs, other times they don’t respond to any drugs at all.

The reality is that superbugs aren’t a special kind of virus or bacteria; any virus or bacteria can become a superbug given the right selection pressures.

We’ll use bacteria as an example. If a colony of bacteria is exposed to antibiotics, usually all the bacteria will die. However, sometimes some bacteria in that colony will have a mutation that makes them resistant to the antibiotics. Before, bacteria with that mutation may have made up only a small part of the bacteria population. However, once antibiotics remove all the non-resistant bacteria, the surviving resistant bacteria will reproduce and make up the entire population.

Essentially, over time the use of antibiotics selects for the bacteria that are most strongly resistant to antibiotics. If antibiotics are used correctly and judiciously the development of superbugs is uncommon. However, if antibiotics are prescribed too often or for problems when they aren’t needed, it makes the creation of superbugs much more likely.

Although viruses can’t reproduce themselves and must instead use the machinery of host cells to replicate, the same basic idea applies. Prolonged use of antiviral medications can select for resistant strains of virus and eventually make them more common.

Superbugs are part of the reason that research and development of new antibacterial and antiviral drugs are so important. It’s also vitally important to avoid the overuse of antimicrobial drugs so they can retain their effectiveness as long as possible.