What Is The Difference Between Bacterial And Viral Infections?

The majority of illnesses in the world are caused by infections, especially bacteria and viruses. Bacterial and viral infections have a number of things in common they can both make you sick, presenting with similar symptoms, They are often spread in the same way (contact with an infected person, surface, food or water) and cannot be seen with the naked eye.

It is, however, important to know the differences between them because the treatments differ. The major difference between them is that bacterial infections are caused by bacteria, while viral infections are caused by viruses.

Bacteria are single cells that can survive on their own, either inside or outside the body. Most bacteria aren't harmful, and many harmless and helpful bacteria live on your skin and inside your body, especially in the gut. Only a few bacteria are harmful.

Viruses are smaller than bacteria, and they need a living host like a human or animal to grow and multiply. This means that they cause infections by entering and multiplying inside the body's healthy cells.

In this article, you would learn more about the differences between bacterial and viral infections, as well as the diagnosis and treatments for each of them.


The difference between bacterial and viral infections

As stated above, bacterial and viral infections present with similar symptoms which can make it a bit difficult to differentiate between the causative organism. Symptoms such as coughing and sneezing, fever, inflammation, vomiting, diarrhoea, fatigue, and cramping are common with them.

Bacterial infections

Bacterial infections are caused by single-celled microorganisms that have the ability to survive in different types of environments. Bacteria can survive on surfaces, door handles, inside the body, and even in extreme temperatures. Almost all bacteria are harmless to humans, and some even help digestion, kill disease-causing bacteria, provide essential nutrients, and fight cancer cells.

Fewer than 1% of bacteria cause diseases in people and are referred to as pathogenic bacteria. A bacterial infection occurs when bacteria have evolved to evade or manipulate the body’s immune system, causing infections like:

Infections caused by bacteria include:

  • Many urinary tract infections
  • Strep throat
  • Typhoid
  • Tuberculosis
  • Tetanus
  • Bacterial pneumonia

Viral infections

Viral infections are caused by microorganisms that are even smaller than bacteria. To grow and multiply, they require living hosts, such as people, plants, or animals. As soon as a virus enters your body, it attaches itself to one or more cells and takes control of its machinery so that it can produce more viruses.

Unlike bacteria, most viruses are harmful and cause disease. They are also specific about the cells they attack. Viruses, for instance, attack the liver, respiratory, and blood cells.

Diseases caused by viruses include:

  • The common cold/flu
  • Chickenpox
  • Coronaviruses
  • Hepatitis B
  • Herpes
  • Human Papillomavirus
  • HIV, which can lead to AIDS

Bacteria and viruses are transmitted by:

  • Cuts, contaminated food, or water
  • Exposure to infected bodily fluids through activities such as sexual intercourse or sharing needles.
  • Touching contaminated surfaces like door handles, taps, toys and flat surfaces.
  • Close contact with an infected person
  • Contact with the faeces of an infected person
  • Inhaling the exhaled droplets of someone who is infected while coughing or sneezing
  • Bites from infected animals or insects

Diagnosis of bacterial and viral infections

At times, it can be a little difficult to know if an infection is caused by bacteria or a virus. This is because a number of infections (like diarrhoea, meningitis, and pneumonia) can be caused by either. If you think you have a bacterial or viral infection, you should consult your healthcare provider. A prompt diagnosis is very important.

Bacterial infections

To diagnose a bacterial infection, your healthcare provider will first listen to your symptoms, and might examine you (listen to your heart and lungs, feel your abdomen, look at your skin).

If necessary, your healthcare provider might send one or more of your body fluids (blood, phlegm, urine, stool or tissue samples) to a lab to identify the causative organism.

Viral infections

A healthcare provider can diagnose you with a viral infection based on your symptoms and physical examination. Your provider may take a blood sample or swab your nose and throat to diagnose a particular virus.

If they think you have a viral infection causing serious inflammation in your lungs, brain, or another internal organ, your provider might send for X-rays, ultrasound, MRI, or CT imaging. 

While imaging can't diagnose a viral infection, it can help your provider understand how it affects your body.

Your provider might send body fluid or tissue samples (blood, saliva, phlegm, urine, stool, cells from your cervix)  to a lab to look for signs of a viral infection (viral DNA/RNA, antibodies, or antigens).

Treatment for bacterial and viral infections

Bacterial infections

Many bacterial infections often go away on their own without antibiotics. If your body is unable to fight off a bacterial infection, you may need prescription antibiotics. Depending on where your infection is and how serious it is, antibiotics can be prescribed for use:

  • Orally (Liquid, capsule, tablet)
  • Topically (Ointment or cream, spray)
  • By intravenous (IV) therapy
  • In the eyes and ears (Eyedrops and eardrops)

Sadly, because bacteria are highly adaptable, a great number of them have developed resistance to antibiotics, and would not be eliminated by antibiotics that would normally get rid of them. Antibiotic abuse is a major cause of antibiotic resistance.

Viral infections

The treatment of viral infections has proved more challenging, mainly because viruses are really tiny and reproduce inside cells. For viruses that can cause life-threatening or chronic illnesses, your healthcare provider may prescribe antiviral medications or treatment that prevents you from getting sick after being exposed to a virus.

When you have a viral infection like the common cold that seldom results in serious disease, you may typically treat the symptoms at home while you wait for them to go away on their own.

Antiviral medications

Antiviral medications stop viruses from making replicating. They can shorten the duration of some respiratory infections or treat chronic infections. Antiviral medications are usually specific. This means that they can only treat one type of virus, and don’t work on other viruses.

Post-exposure prophylaxis (prevention)

This type of treatment prevents you from getting sick after being exposed to the virus. A healthcare provider has to administer these treatments before you begin to have symptoms. These include antiviral medications and immunoglobulin (antibody) treatment. Post-exposure prophylaxis is available for HIV, Rabies, Hepatitis B, and Chickenpox.

Convalescent plasma therapy

If an individual has a life-threatening viral infection, he can be treated with a blood transfusion. In convalescent plasma treatment, blood is donated by a person who has recovered from an infection with the same virus. The plasma from the blood is then administered to you by your healthcare professional via an IV. Antibodies found in the plasma aid in the body's defense against infection.


Bacterial and viral infections are common. They can be prevented by practicing good personal and food hygiene. Antibiotics are not effective against viral infections. You should also avoid popping antibiotic pills before ascertaining that you have a bacterial infection.


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This content is purely informational and isn’t medical guidance. It shouldn’t replace professional medical counsel. Always consult your physician regarding treatment risks and benefits. See our editorial standards for more details.

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Godswill Samson

BSc, Pharmacology, University of Lagos, Nigeria

Godswill is a budding health writer with a passion for health and wellness. She combines this with her writing skill to educate the public on ways to live fuller and healthier lives.

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