What Is Bacterial Infection


Bacteria are single-celled microorganisms. Although we tend to think of disease and illness among other things when we think of bacteria, although not  all bacteria are harmful. Bacteria are found basically everywhere on earth.1 Our bodies too are full of bacteria, some are very helpful like bacteria found in the gut that helps with digestion.2 

On the other hand, there is a small percentage of bacteria that are  harmful and do in fact cause diseases and infections when they enter your body. These bacterial infections can affect almost any part of your body. You can get a bacterial infection in your brain, lungs, skin, and practically in all  the organs in your body.3 Bacterial infections are caused by bacteria and therefore differ from viral infections. 

Bacteria can live and survive in a variety of different conditions and locations such as in water, soil, or living in other organisms. Therefore, it is very easy to come into contact with potentially harmful bacteria if you are not careful. Bacteria reproduce by dividing in a process called binary fissure, this allows them to increase their numbers very quickly.2 For some infections, it only takes a small number of bacteria to enter your system before you start to see the effects. Whereas other infections require a lot more bacteria to enter your body to cause an infection or disease. 

Causes of bacterial infection

For bacteria to cause an infection, it first has to enter your body. This can either be through your mouth, through your nose, a cut or a wound, through insect bites, or essentially anywhere where there’s an entry opening for the bacteria.4 Once in your system, the disease comes about because of one of two things:

  • The bacteria itself and what it does when it enters your body 
  • How your body responds to the bacteria (i.e. the immune response)2 

Bacteria can be spread or transmitted through several mediums; for example:

  • Contact
  • Water
  • Soil
  • Food
  • Vectors (infected animals or insects)
  • Air2

For an infection to occur, the bacteria first need to enter your body. This can be through your mouth, a cut/wound, or through your nose or eyes. According to Cleveland Clinic, there are several ways in which you can get bacterial infections:

  • Touching dirty/contaminated surfaces (toilet seats, dirty phones, etc)
  • Eating contaminated food
  • Drinking water from contaminated sources/ drinking water that is not clean
  • From getting bitten by an infected insect
  • Through close contact with other people
  • Through inhaling contaminated air (e.g inhaling someone’s cough droplets)
  • Through vaginal, or oral sex
  • From surgery

Some places are more likely to be breeding grounds for bacteria compared to others. For example, a hospital where lots of people get  sick, is likely to host a lot of bacteria if kept unclean. That is why it is very important to keep the hospital very clean, to wash your hands after visiting a hospital and it is important that equipment used in a hospital is kept clean or sterilized

Bacteria tend to have a preference/bias as to which parts of your body they will infect. For example, Neisseria meningitidis will either infect your meninges and cause bacterial meningitis.  Alternatively,  the same bacteria can infect your lungs and cause pneumonia.2 However, you won’t see this bacteria causing a bacterial infection in your skin.

Signs and symptoms of bacterial infection

Signs and symptoms of a bacterial infection vary depending on the site  of infection. There are, however, some common symptoms that are likely to occur with almost any bacterial infection. These are:

  • Fever
  • Chills
  • Tiredness
  • Headache3

Other symptoms include:

  • Blocked/stuffy nose
  • Stiff neck
  • Diarrhea
  • Vomiting
  • Abdominal pain
  • Shortness of breath
  • Pain or a burning sensation when urinating5

Management of bacterial infection

Some bacterial infections are self-limiting, meaning that they will go away on their own. For other infections, your healthcare provider may prescribe antibiotics to help fight off the bacterial infection.2 It is very important to only take antibiotics when prescribed due to the increasing public health concern of antibiotic resistance. Antibiotic resistance is essentially when antibiotics become less effective in fighting off infections, because of how people have misused antibiotics. The bacteria can now actually fight off/resist the effects of the antibiotics, meaning that the antibiotics no longer work as well or at all. 

Key things to remember when taking antibiotics:

  • Only take when prescribed
  • Don’t skip doses
  • Take your full antibiotic course (even if you are feeling better)


How is  a bacterial infection diagnosed

To diagnose your bacterial infection, your healthcare provider will ask you a series of questions relating to how you have been feeling, what symptoms you have been getting, and for how long. They may also do physical examinations such as listening to your heart and lungs (depending on where the infection is) or take body fluid or tissue samples that will be taken to a lab and tested. 

These samples may include:

  • Blood
  • Urine
  • Phlegm 
  • Eye fluid
  • Fluid around your brain and spinal cord
  • Skin or other tissue that is suspected to be affected3

Some areas of the body may require imaging to determine if you have a bacterial infection such as CT scans, MRIs or X-rays, or ultrasounds  for bacterial infections of internal organs, e.g.,  brain, and lungs.

What are the types of bacterial infection

There are several types of bacterial infections , and these can affect different parts of your body. Some types of bacterial infection include:

Some bacterial infections are referred to as ‘secondary infections.’ These are infections that you get when your body’s immune system is already weak/compromised due to you having contracted another illness e.g. COVID-19 or pneumonia. This makes your body more susceptible to bacterial infections. 

How can I prevent bacterial infection

Some infections cannot necessarily be prevented. However, in many cases, there are several things that you can do to prevent the spread of bacteria and avoid it entering your body. Most of these methods involve keeping your personal hygiene intact:

  • Wash your hands after using the bathroom
  • Wash your hands before cooking food and before eating
  • Do not share personal items such as razors, needles, and toothbrushes
  • If you have a wound or a cut, keep it clean and cover it with a plaster or bandage
  • Use a condom during sex
  • Stay at home if you are sick
  • Protect yourself from any insect/bug bites
  • Keep any wounds/cuts covered and clean
  • Make sure you eat a healthy, balanced diet (so that your body is sufficiently nourished and can fight off infections)

Who are at risk of bacterial infection

Certain factors increase the likelihood of bacteria thriving  in your body and cause disease to develop. These are called risk factors and include:

  • Genetic makeup
  • Nutritional status: if you aren’t sufficiently nourished you won’t have enough energy to fight off the infection or the correct nutrients needed to support your immune system
  • Age: the strength or efficiency of our immune system can decline with age,
  • Coexisting illnesses: if you already have an illness e.g.,  Covid-19 or pneumonia then your immune system may be compromised/weaker as it is already fighting an illness. Therefore, you may be susceptible to having a bacterial infection
  • Environment: living in areas with air pollution or where there are chemicals and contaminants in water, soil, or surrounding areas can increase your risk of developing a bacterial infection

How common is bacterial infection

In a 2019 study carried out by GRAM (a partnership between the University of Oxford and the Institute of Health Metrics and Evaluation), it was found that 1 in 8 deaths worldwide was linked to common bacterial infections. This equates to a total of 7.7 million deaths associated with 33 common bacterial infections. In high-income countries, bacterial infections accounted for 52 deaths per 100 000 compared to 230 deaths per 100 000 in low-income countries. 

The 3 types of infection that accounted for the majority of the deaths were:

  • Bloodstream infections
  • Lower respiratory infections such as pneumonia
  • Peritoneal and intra-abdominal infections6,7

When should I see a doctor

Contact your doctor or healthcare provider if you are experiencing persistent symptoms of a bacterial infection (persistent fever, persistent cough, unexplained redness of the skin). Leaving an infection for too long before seeing your doctor can result in developing sepsis, a life-threatening condition. 

Visit the emergency room if you experience any of the following:


Bacterial infections are a leading cause of death worldwide and are caused when harmful bacteria enter your body and trigger your immune system. The spread of bacteria can be minimized  by staying on top of your personal hygiene via adopting habits such as washing your hands regularly and avoiding sharing personal items. Symptoms of bacterial infection include fever, chills, headache, vomiting, or nausea. If these symptoms persist, contact your healthcare provider, do not leave it too long to avoid developing serious/devastating complications. 


  1. Graham BJ. Bacteria [Internet]. Genome.gov. National Human Genome Research Institute; 2019. Available from: https://www.genome.gov/genetics-glossary/Bacteria
  2. Doron S, Gorbach SL. Bacterial Infections: Overview. International Encyclopedia of Public Health [Internet]. 2008 Aug 26;273–82. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7149789
  3. Cleveland Clinic. Bacterial Infection: Causes, Symptoms, Treatment & Prevention [Internet]. Cleveland Clinic. 2022. Available from: https://my.clevelandclinic.org/health/diseases/24189-bacterial-infection
  4. Sepsis Alliance. Bacterial Infections [Internet]. Sepsis Alliance. 2022. Available from: https://www.sepsis.org/sepsisand/bacterial-infections/
  5. CDC. Know the Signs and Symptoms of Infection [Internet]. Centers for Disease Control And Prevention. 2019. Available from: https://www.cdc.gov/cancer/preventinfections/symptoms.htm
  6. Murray CJ, Ikuta KS, Sharara F, Swetschinski L, Aguilar GR, Gray A, et al. Global Burden of Bacterial Antimicrobial Resistance in 2019: A Systematic Analysis. The Lancet. 2022 Jan 19;399(10325):629–55. Available from; https://pubmed.ncbi.nlm.nih.gov/35065702/
  7. Vos T, Lim SS, Abbafati C, Abbas KM, Abbasi M, Abbasifard M, et al. Global Burden of 369 Diseases and Injuries in 204 Countries and Territories, 1990–2019: a Systematic Analysis for the Global Burden of Disease Study 2019. The Lancet. 2020 Oct 17;396(10258):1204–22. Available from; https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30925-9/fulltext
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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