Enable JavaScript to visit this website.

The Difference between Bacteria and Viruses

Bacteria and viruses can cause many different types of illnesses in humans. An antibiotic is a medication used specifically to treat bacterial infections. Antibiotics work by attacking the structures and functions inside bacterial cells, but have no effect against viruses. Your doctor will not prescribe antibiotics to treat a viral infection or illness not caused by bacteria.

When do antibiotics work?

Antibiotics kill or reduce the growth of bacteria by attaching to specific targets on, or within the bacteria. Viruses are constructed differently from bacteria – a virus must get inside a living cell to grow and replicate. (1)

  • Antibiotics do not work against viruses because they have no target to attack in a virus.
  • Taking antibiotics for a viral infection doesn’t kill the virus, but contributes to antibiotic resistance (2)

Bacterial Vs Viral Infections (3-5)

Note: The listed illnesses are examples; do not consider this to be a medical advice. Please consult your clinician for the most appropriate treatment.


  1. Centers for Disease Control and Prevention. Antibiotic resistance threats in the United States, 2013.
    Available at: www.cdc.gov/drugresistance/pdf/ar-threats-2013-508.pdf. Accessed 26 December 2018.
  2. Laxminarayan R, et al. Antibiotic resistance – the need for global solutions. Lancet Infect Dis 2013;13:1057-1098.
  3. Centers for Disease Control and Prevention. Viruses or bacteria. What’s got you sick?
    Available at: www.cdc.gov/antibiotic-use/community/pdfs/Viruses-or-Bacteria-Factsheet-Eng.pdf. Accessed 26 December 2018
  4. Centers for Disease Control and Prevention. Antibiotic resistance questions and answers.
    Available at:www.cdc.gov/getsmart/community/about/antibiotic-resistance-faqs.html. Accessed 26 December 2018.
  5. Centers for Disease Control and Prevention. Antibiotics aren’t always the answer.
    Available at: www.cdc.gov/features/getsmart/index.html. Accessed 26 December 2018.

PP-CPF-IND-0008 | 11th January 2019