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What is the difference between bacteria and viruses?

What is the difference between bacteria and viruses?

Bacteria and viruses are both tiny, microscopic organisms that can make you sick. But what is the difference between these two types of germs? Bacteria are single cells that can multiply and cause infection. Viruses are much smaller than bacteria and need a host cell to reproduce. Viruses can only infect living cells, while bacteria can also infect non-living things like soil or water. Both bacteria and viruses can cause infectious diseases, but viruses are often more deadly. Terms like viruses, bacteria and germs have been used a lot since the coronavirus pandemic. Understanding the differences between bacteria and viruses is important for protecting your health.

What are the 3 major differences between viruses and bacteria ?

Viruses – living or not living?

Viruses are small infectious particles and are not living organisms. They can only grow when they’re in contact with living cells. They don’t have the ability to divide on their own and need an external force for sustenance, like host animals or plants who provide them nutrients while there’s no oxygen available (this is what gives viruses life). The virus only comes alive when it envelops its genetic material in cells of other living things so that’s why some viruses attack plants while others only affect animals or humans. Viruses do not contain a cell wall so their genetic material (RNA or DNA) is enveloped by a protein coat.

Bacteria – living or not living?

These single-celled microorganisms are everywhere, they are living organisms that can be found on our skin or inside of our bodies. Their shapes vary, and doctors use these characteristics to separate them into groups. Bacterial cells have cell walls and everything they need to live including DNA and cellular structures which produce protein. Due to their cell walls, bacteria can multiply by binary fission. The simple metabolism of these microbes provides enough energy for them so as long as there is food around them populations will continue growing.

Size of bacteria and viruses

Both bacteria and viruses are microscopic and invisible to the naked eye but differ in size. Viruses are 10 to 100 times smaller than the smallest bacteria. To put it another way, bacteria can be described as giants next to viruses!

Mode of living and reproducing

Mode of living and reproducing for viruses

All viruses are unable to replicate on their own. They need living hosts such as the human body, plants or animals. They have to enter a living cell of a host and take over the cell’s processes for making new genetic material and proteins. The cell copies the viral genetic material and makes new viral genetic material and proteins. These components assemble into new viruses, which escape from the cell. Some types of viruses cause the complete breakdown of the cell. Other types of viruses leave by pushing through the cell membrane. Both methods damage the cells and this causes disease. The viruses that have left the cell can go on to infect other cells.

Mode of living and reproducing for bacteria

Bacteria are small, single-celled organisms that occur naturally in nearly every environment on Earth. Many people think of bacteria as harmful microorganisms that cause diseases, but there are many different types of bacteria, some of which are beneficial to humans.

In terms of reproduction, bacteria generally reproduce through a process called binary fission. This process begins when the bacterium’s cell walls split in half, creating two separate cells. These cells then grow and divide, creating a new generation of bacteria. This process can happen very quickly, with some bacteria able to double their numbers every few minutes. For binary fission to occur, the bacterium must first reproduce its DNA. It then builds a new cell wall around the DNA, creating two separate cells. The parent bacterium then splits into two, each with its own set of DNA and cell wall. Binary fission is an extremely efficient way for bacteria to reproduce, and it allows them to quickly adapt to new environments and changes in their surroundings.

Are there any similarities between bacteria and viruses?

Yes, in their transmission. Both these pathogens can be spread in similar ways to cause disease:

  • Droplets expelled during coughs/sneezes
  • Close contact with an infectious person (a handshake could transmit germs)
  • Touching your nose, mouth, or eyes after contact with an infected surface ( while handling groceries for example- then proceed on to other tasks without washing hands thoroughly beforehand)
  • Contact with infected body fluids through kissing, sex, urine, or faeces
  • Contact with infected animals or insects such as fleas, ticks, or mosquitoes
  • Transmission from mother to child during birth.

Examples of how infections can spread

Infections such as colds, flu and tuberculosis cause a person to sneeze or cough. This sends droplets containing pathogens into the air. Once in the air, flu viruses can survive for about a day. However, tuberculosis can survive for months in the air and mix with dust that can blow around and infect another person.

Some pathogens spread in water, such as the bacteria that cause cholera and typhoid. We rarely see these diseases because our water is treated to kill pathogens.

Pathogens of the digestive system can spread in food as well as water causing food poisoning. They enter the body through the mouth. Helicobacter bacteria are thought to be spread when people touch other people’s food after touching their mouths or after going to the toilet. The bacteria may also spread on the feet of flies that have fed on infected faeces and landed on food.

How are bacterial and viral infections diagnosed?

It can be difficult to know what causes an infection because viral and bacterial infections can cause similar symptoms and some conditions such as meningitis can be caused by either. It is important to know whether bacteria or viruses cause an infection because the treatments differ.

To determine the cause of your infection your doctor will:

  • Take your medical history
  • Carry out a physical examination
  • Carry out a blood or urine test
  • In rare cases take a sample of tissue for testing


Your immune system is equipped to fight off many infectious diseases without treatment. However, if you have a weakened immune system or when the pathogen reproduces faster than the immune system can control it, it begins to harm the body and medication is needed.

Viral infections

Vaccines prevent the spread of viral infections. Antiviral medications help to slow down the reproduction of viruses but can not stop it completely. Antibiotics are ineffective against viruses.

Examples of viral infections include the flu, herpes simplex virus, chickenpox, the common cold, hepatitis A, hepatitis B, Ebola virus, human papillomavirus (HPV) and HIV/aids.

Bacterial infections

Antibiotics are used to control bacterial infections. Antivirals are not effective against bacteria.

Examples of bacterial infections include whooping cough, strep throat, ear infections and urinary tract infections.

Now that we’ve taken a look at the two different types of organisms, bacteria and viruses, it’s important to understand that they both need to be treated differently. Bacteria are living things and as such can be killed with antibiotics. However, viruses are not living organisms and cannot be killed with antibiotics- in fact, using antibiotics when you have a viral infection can make your illness worse. Speak to your healthcare professional for medical advice on how to treat an infection caused by bacteria or viruses.


Medical Disclaimer

NowPatient has taken all reasonable steps to ensure that all material is factually accurate, complete, and current. However, the knowledge and experience of a qualified healthcare professional should always be sought after instead of using the information in this page. Before taking any drug, you should always speak to your doctor or another qualified healthcare provider.

The information provided here about medications is subject to change and is not meant to include all uses, precautions, warnings, directions, drug interactions, allergic reactions, or negative effects. The absence of warnings or other information for a particular medication does not imply that the medication or medication combination is appropriate for all patients or for all possible purposes.

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