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Bacteria and virus: Differences you need to know

Bacteria and virus: Differences you need to know
LifeScience3 min read
  • Two different classes of micro-organisms inhabiting the earth, bacteria, and viruses, have nothing in common between them other than sharing the name ‘microbes’.

  • Bacterial and viral infections can cause mild, moderate, or severe diseases in humans with similar or dissimilar symptoms.

  • Bacterial and viral infections are different in many regards, as these microbes have stark structural differences, and they respond differently to medications.
Even before the COVID-19 pandemic, diseases caused by bacteria and viruses have been a popular topic in human society. Disease outbreaks like Black Death and Bubonic Plague caused by Yersinia Pestis bacteria and smallpox caused by the variola virus have killed millions of people.

The entire world suffered a fatal blow after two big pandemics. One during 1918-19 called the Spanish Flu, which killed 20-40 million people. The second being the 2013 HIV / AIDS outbreak, which killed around 1.5 million people.

What are bacteria and viruses?

Bacteria and viruses are two different classes of microorganisms. Both are too small in size to be seen without the aid of a powerful microscope. Nevertheless, they are as different from each other.

Point of comparison



Anatomical features

Bacteria are complex single-celled organisms consisting of a cell-wall and an elastic membrane surrounding the cell fluid. Bacteria come in different shapes and sizes including spheres, cylinders, threads, rods, and chains. The projections on bacteria are known as pili or flagella that help them attach to the host and move respectively.

Viruses are much tinier than bacteria. The largest virus is still smaller than the smallest of bacteria. The structure of a virus reveals a piece of genetic material either DNA or RNA surrounded by a protein shell known as a capsid. Many viruses have some projections called as peplomers that help them attach to some kinds of receptors on the host cell.


Can exist, live and reproduce on their own. They can live in any conceivable environment, and inside or outside the human body.

Viruses are parasitic. They cannot survive without a host. They can multiply only by attaching themselves to living cells.

How harmful they are to humans

Most bacteria are harmless. Many bacterial populations in fact help humans by digesting food and killing disease-causing microbes and cancer cells and supplying essential nutrients. Only less than 1% of bacteria called pathogenic bacteria cause diseases in people.

Most viruses are disease causing. In several cases, they reprogram the cells they inhabit to create new viruses to the point of the host cells bursting and dying. In some other cases, they convert normal cells into cancerous or malignant cells.


Bacterial infections are treated by administering antibiotics. Overuse of antibiotics can make the bacteria develop resistance to them.

Antibiotics are not effective in treating viruses. Most viruses are fought through vaccines. Due to their smaller size, viruses are highly challenging to treat. In some cases, antiviral medications are employed. Some viruses have become drug-resistant.