Bacterial Diseases in Humans

Habish Ribin Haneef
Updated on

Bacteria are tiny single-celled organisms and are found almost everywhere on Earth. Bacteria are very imperative to the planet’s ecosystems. Some species of bacteria can even survive under extreme conditions of temperature and pressure. Another astonishing fact is that the human body consists of more bacterial cells than human cells. But don’t worry, most bacteria in the human body are harmless and some of them are even helpful. For example, some bacteria in our body help to digest substances that the human body cannot break down such as carbohydrates and short-chain fatty acids. Only a small percentage of bacteria are harmful to humans and these are the species that cause diseases. The bacterial species that induce diseases in humans are called pathogens. Bacteria are of different shapes, they can be spheres, rods, or spirals.

In this blog, let’s discuss some diseases caused by pathogenic species of bacteria.



Cholera is a bacterial infection spread through contaminated food and water. The bacterium “Vibrio Cholerae” causes this disease. Cholera is one of the most dangerous diseases caused by bacteria. If not provided proper healthcare, cholera can be fatal and may be worse even in healthy people. Industrialized countries have virtually eradicated cholera thanks to modern sewage and water treatment. But, the infection is still common in regions with poor sanitation and unclean water. Africa, Southeast Asia, and Haiti are places where cholera still has an edge. The symptoms of cholera include diarrhea, nausea and vomiting, and dehydration. Washing your hands with soap and water frequently, having food that is completely cooked and hot, drinking hot and safe water, and sticking to fruits and vegetables will almost keep you away from cholera.

Typhoid Fever


Typhoid fever is another bacterial infection spread through contaminated food and water. Like cholera, if not provided proper treatment, typhoid can also be fatal. The infection is caused by the “Salmonella Typhi” bacterium. Typhoid fever is more common in regions with poor sanitation and unclean water. Children are believed to be most at risk of getting typhoid fever as their immune system is still developing. Typhoid fever is more common in the Indian subcontinent, Africa, South and Southeast Asia, and South America. The symptoms of typhoid fever include high fever, headache, aches and pains, fatigue, cough, and constipation. Typhoid fever can be prevented by using the same preventive measures used to prevent cholera.



Tuberculosis (TB) is an infectious disease caused by the bacterium “Mycobacterium Tuberculosis”. TB is an airborne disease that is spread through tiny droplets when an infected person coughs or sneezes. This infection mainly affects the lungs. According to the immunity of your body, doctors classify tuberculosis into latent TB and active TB. In latent TB, the bacteria in your body are inactive and cause no symptoms. But, sometimes, latent TB may be transformed into active TB and if that occurs, proper treatment is necessary. On the other hand, active TB leads you to sickness and includes symptoms like high fever, coughing for three or more weeks, coughing out blood or mucus, chest pain, pain while breathing and coughing, weight loss, fatigue, chills, night sweats, and loss of appetite. Avoiding close contact with an infected person is the main way to get away from TB. Antibiotics are also prescribed for the treatment of TB.



Pneumonia is an infection that affects one or both lungs. Pneumonia can be caused by bacteria, viruses, or fungi. Pneumonia leads to inflammation in the air sacs of the lungs, called alveoli. As a result of this, alveoli will be filled with fluid or pus ultimately making it difficult to breathe. Both bacterial and viral pneumonia can be contagious. Yes, bacterial and viral pneumonia is spread from person to person through tiny droplets when an infected person coughs or sneezes. Pneumonia can also be spread through contact with surfaces or objects contaminated with the causative microbe. Fungal pneumonia does not spread from person to person. This type of pneumonia can be contracted from the environment. Anyways, let’s talk about bacterial pneumonia. Bacterial pneumonia is caused by several bacteria the most being “Streptococcus Pnumoniae”. Other bacteria causing pneumonia include “Mycoplasma Pnumoniae”, “Haemophilus Influenzae”, and “Legionella Pneumophila”. The symptoms include fever, headache, coughing that may produce mucus, sweating or chills, chest pain(the pain may be serious while coughing or breathing), fatigue and tiredness, loss of appetite, nausea and vomiting, and shortness of breath(while doing normal activities or even while resting). Pneumonia can be prevented by using a vaccine nemed pneumococcal vaccine and certain antibiotics can also be used for the treatment of pneumonia.



Leptospirosis is a bacterial disease caused by the bacterium “Leptospira”. The infection is mainly spread through the urine of infected animals such as cattle, pigs, horses, dogs, rodents, wild animals, etc. This urine can get into water or soil and remains there for weeks to months. If anyone comes in contact with this urine, they may get infected. The microbe enters the human body through skin or mucous membranes especially when the skin is ruptured from cuts, scratches, or wounds. Leptospirosis outbreaks usually occur due to contact with water contaminated with urine of infected animals such as floodwater. The symptoms of leptospirosis include high fever, headache, muscle aches, chills, vomiting, jaundice, red eyes, abdominal pain, diarrhea, and rashes. Leptospirosis can be treated with antibiotics like doxycyclin or penicillin. But for patients with severe symptoms, intravenous antibiotics may be required. The main preventive measure for leptospirosis is avoiding contact with water contaminated with animal urine. If in case, you are exposed to certain water bodies, always wear protective clothing and footwear. Yes, maintaining a good health and hygeine is the main method to get away from this dreaded infection.



Syphilis is a chronic bacterial infection caused by the bacterium “Treponema Pallidum”. The infection is transmitted through sexual contact. The only way the infection is transmitted is through direct contact with syphilis sores that develop in the mouth, penis, vagina, or anus. Babys can also get the infection if their mother is infected with syphilis and this is called congenital syphilis. Though rare, syphilis can also be transmitted through bood transfusions. If not provided proper healthcare, according to the progress of the infection, the patient’s important organs like brain and heart will undergo serious damage. People having sex without condoms and other barriers and people who have HIV are the most at the risk of syphilis. There are four stages of syphilis- primary, secondary, latent, and tertiary. If treated earlier, the infection can be prevented in the primary or secondary stage itself. But if failed to do so, the infection will progress and will ultimately reach the most dangerous tertiary stage that can be life-threatening. The disease starts with the primary stage where a small, round sore called chancre develops. Next is the secondary stage where skin rashes and sore throat may develop. The rashes can develop on any part of the body. Other symptoms of secondary stage include fever, headache, swollen lymph nodes, fatigue, weight loss, aching joints, and hair loss. In latent stage, the symptoms from the earlier two stages disappears and there will be no noticeable symptoms. But still, the microbe remains in the body and this stage may last for years before moving to the last and final stage, the tertiary stage. Tertiary stage occurs years or decades after the primary stage. This stage can be life-threatening and it’s symptoms include blindness, loss of hearing, memory loss, heart disease, neurosyphilis, stroke, meningitis, damage of soft tissue and bone, and mental health conditions.



Tetanus is a bacterial infection caused by the bacterium “Clostridium Tetani”. The disease is spread through contaminated fecal matter, animal bites, or contaminated saliva. Tetanus is also called “lockjaw” because people affected by this infection can’t open their mouth properly and hence it makes it very difficult for them to swallow something. This occurs because, after entering the host body, the bacteria produces a toxin that causes painful muscle contractions. This paralyzes the nervous system and muscles of the patient. The symptoms of the infection include fever, headache, painful muscle stiffness throughout the body, trouble swallowing, changes in heart rate and blood pressure, sweating, jaw cramping, and sudden involuntary muscle spasms, often in the stomach. There are various ways to treat the infection including antibiotics, drugs to control muscle spasms, and immediate treatment with medicine called human tetanus immune globulin (TIG).



Plague is a bacterial infection that affects humans and animals. The disease is caused by the bacterium “Yersinia Pestis”. The disease is transmitted to humans through the bite of infected rodent flea or other animals. The symptoms of the infection include high fever, headache, chills, cough, nausea, swelling in lymph nodes, and chest pain. Plague is known for killing millions of people in Europe during the middle ages. But, today antibiotics are very effective in overtaking plague. If no proper healthcare is given, the infection can be serious and life-threatening. Today, more cases of plague occurs in parts of Africa and Asia and in rural areas of Western United States.c



Gonorrhea is a sexually transmitted bacterial infection caused by the bacterium “Neisseria Gonorrhoeae”. If not treated early, the infection can cause serious complications in both men and women. The infection mainly affects the urethra, rectum, or throat. The symptoms of gonorrhea in men include painful urination, pus-like discharge from the tip of the penis, and pain or swelling in one testicle. The symptoms of gonorrhea in women include increased vaginal discharge, painful urination, bleeding from vagina during periods, and abdominal or pelvic pain. The same methods of prevention used to prevent syphilis is also applicable here.

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Answer. Tetanus is also called “lockjaw” because people affected by this infection can’t open their mouth properly and hence it makes it very difficult for them to swallow something.

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