Why Don't Antibiotics Work On Viral Infections?

By Susanna Redmer on May 27 2020 in Answer

Antibiotics are commonly used throughout the world to treat and prevent disease caused by bacterial infections.
Antibiotics are commonly used throughout the world to treat and prevent disease caused by bacterial infections.
  • Bacteria and viruses replicate differently.
  • Viruses must attach to a host cell to replicate.
  • Scientists have only developed a handful of antivirals.

Antibiotics are one of the most important way to fight against a bacterial infection. Antibiotics are commonly used throughout the world to treat and prevent diseases caused by bacterial infections. They are used to treat ailments like strep throat, whooping cough, urinary tract infections, and sepsis. They kill bacteria or stop bacterial growth, but they do not work against viruses like those responsible for common cold, influenza, or even COVID-19. Bacteria have quite different structures than viruses. Read through the following paragraphs to find out more about why antibiotics do not work against viral infections.

Viruses are spread from one person to another through coughs, sneezes, vomit, bites from infected animals or insects, and exposure to infected body fluids through sexual intercourse or sharing hypodermic needles.

Viruses work differently than bacteria. Viruses live and replicate inside of a human cell and are not able to survive out of that environment. Viruses embed their genetic material into a human cell’s DNA, so they can reproduce. Viruses harness human cells to carry out their own functions.

Why Abtibacterials Don't Work on Viruses

The common cold is caused by a virus and cannot be treated by antibiotics.

The following points explain why antibiotics do not work against viruses.

  1. Viruses have different structures and replicate in different ways than bacteria.
  2. Antibiotics target the growth machinery in bacteria so that they cannot replicate properly to be effective. Antibiotics essentially kill bacteria.
  3. If you look a virus’s structure, antibiotics will not work to kill a virus since it has a completely different replicating machinery.

Unfortunately, there are many illnesses caused by viruses that antibiotics do not help. Illnesses like most sore throats, cold and runny noses, acute sinusitis, acute bronchitis respiratory syncytial virus (RSV), some eye and ear infections, and the flu. Despite viral illnesses not being able to be treated by an antibiotic, most are “self-limiting," meaning a person’s own immune system will fight the virus. It may take 7 to 10 days to fight a cough or cold, and the flu can take up to two weeks or longer to recover from. Over-the-counter medications, such as Tylenol may help alleviate some of the symptoms of a viral infection.

Viruses can be difficult for the human immune system to fight because they enter the cells of a human’s body. T-lymphocytes, a type of white blood cell in a human’s immune system, can find cells that have been infiltrated by a virus because the surface of the cells looks different when the virus begins to replicate.


Some viral infections like the flu, shingles, or chickenpox may require an antiviral drug which need to be prescribed by your doctor. These drugs shorten the duration of the infection and prevent complications from the virus. They work best when they are taken within the first 24 to 48 hours of the infection.

In an instance of a complicated or long viral infection, bacteria may also invade the body. This is called a “secondary bacterial infection.” Your doctor may prescribe an antibiotic to kill the invading bacteria. This antibiotic does not treat the virus. One of the best preventive measures against a virus is a vaccine.

Antiviral drugs are only used for a few diseases. They target viral enzymes. Antiviral drugs will work against diseases like influenza, herpes, Hepatitis B and C, shingles, and HIV, but viruses such as Ebola, mild viral meningitis, encephalitis, and others do not have an antiviral drug to use for treatment. Researchers can create laboratory interferon, a naturally occurring protein in the body that an individual can use to fight viral infections. Interferon is used to treat Hepatitis C infections. Another way to protect human beings against viruses is through vaccines.


Vaccines cause your own immune system to produce antibodies. They recognize a virus as a threat and attack it before the viral disease is spread. Vaccines have the potential to eradicate diseases. The World Health Organization headed a massive worldwide campaign to wipe out the smallpox virus.  Mumps, Hepatitis A and B, and chicken pox also have a vaccine against them. However, it is difficult to create a vaccine against a virus like the cold because the disease mutates from one person to the next. The cold viruses would have changed by the time a vaccine against it is created.

There is currently no vaccine against the Covid-19 virus. Scientists are using knowledge derived from past research on Severe Acute Respiratory Syndrome (SARS) and Middle East Respiratory Syndrome (MERS) to develop a vaccine. Scientists are also studying if an individual infected with COVID-19 coronavirus has future immunity against reinfection and for how long it lasts. Human trials of some potential vaccines are also taking place.

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