Why are antibiotics ineffective against viruses?

We are approaching the winter months, the coldest time of the year (at least for those of us living in the northern hemisphere of our planet), and I bet some of us have already caught a cold, a very common infection caused by viruses.

Antibiotics cannot cure colds. However, some people incorrectly believe that antibiotics are effective against cold and other viral infections. Sometimes they feel disappointed when their family doctor does not prescribe antibiotics for them, as they think these medicines can cure all types of infections. But this is not true, it is a misconception.

To shed light on this topic, in this blog I will try to explain why antibiotics are ineffective against viruses.

Let’s start with a key concept: bacteria and viruses are completely different microorganisms.

A bacterium is a microscopic creature consisting of a single cell, enclosed by a capsule and a cell wall, two different protective coatings. Inside the cell, a gooey substance called cytoplasm surrounds the DNA and a number of tiny but vital structures that allow the cell to survive on its own and multiply efficiently.

Antibiotics are powerful medicines. They are designed to target these structures and block the functioning of vital processes, either killing bacteria or stopping them from multiplying. For example, you surely know the antibiotic penicillin. It binds to the structure of the cell wall and disrupts it, thereby destroying the bacterial cell, just as a right key unlocks the door.

A virus is also a simple microorganism, like a bacterium. But be careful: it is not a cell at all! A virus is made up only of genetic material (DNA or RNA) surrounded by a protective shell called capsid, and sometimes another layer. Viruses do not have a cell wall or all the mechanisms that bacteria have in their cytoplasm to multiply. Viruses carry instructions, invade a host cell, and use its structures to produce more copies of the virus.

So, antibiotics are ineffective against viruses, simply because viruses are not cells and do not have those “machineries” that antibiotics specifically target. It is like trying to use the wrong key to open a door. It is a waste of time!

Moving from the electron microscope to everyday life, we can say that antibiotics do not work against viral infections, such as the common cold or flu. Indeed, antibiotics are medicines prescribed only to treat bacterial infections.

Sometimes people use leftover antibiotics for a new infection, basing their decision on their own knowledge and previous experience, often without consulting a physician. However, the new illness may be caused by a virus and may not require an antibiotic therapy at all.

This misuse of antibiotics through self-medication is incorrect and unfortunately is a very common practice today. However, we should understand that using antibiotics for viral infections is like watering fake plants. Or, if you prefer, it is like eating soup with a fork. Pointless.

But there is more, it is even harmful! Misuse and overuse of antibiotics contribute to the development and spread of antibiotic-resistant bacteria, making future infections harder and harder to treat. These precious medications have to be used with care to preserve their effectiveness for when they are really needed. Moreover, an incorrect use can also increase the risk of side effects, interactions with other medicines, and secondary infections, such as Clostridioides difficile (C. diff) infection. In addition, unnecessary antibiotics could also impact on the composition of the normal beneficial bacteria in gut microbiome.

It can be difficult to determine whether an infection is caused by bacteria or viruses. This is why it is always necessary to seek a doctor’s advice when you feel sick. The doctor will perform a physical examination and ask you about your symptoms. Based on this information, he or she may recommend diagnostic tests to make a correct diagnosis, and finally decide on the most appropriate therapy for you.

If your physician detects a bacterial infection, then he or she may recommend an antibiotic therapy. Take these medicines exactly as prescribed for you. Never use leftover antibiotics or share them with other people.

Otherwise, your doctor may conclude that you do not need antibiotics because the infection likely caused by viruses. Do not be disappointed! In this way, you will avoid unnecessary use of these medications and play an important role in the fight against antibiotic resistance.