Bacterial infections are diseases that can affect your skin, lungs, brain, blood and other parts of your body. You get them from single-celled organisms multiplying or releasing toxins in your body. Common bacterial diseases include UTIs, food poisoning, STIs and some skin, sinus and ear infections. They’re often treated with antibiotics.
Bacterial infections are any illness or condition caused by bacterial growth or poisons (toxins). You can get sick from getting harmful bacteria in your skin, gut (GI tract), lungs, heart, brain, blood or anywhere else in your body.
Harmful bacteria from the environment, an infected person or animal, a bug bite or something contaminated (like food, water or surfaces) can cause infections. Bacteria that’s not normally harmful but that gets into a place in your body where it shouldn’t be can also cause infections.
Bacteria are living things with only a single cell that can reproduce quickly. There are millions of bacteria that live all around us — in soil or water and on surfaces in our homes and workplaces. There are even millions of bacteria that live on your skin and inside of your body.
Most bacteria aren’t harmful, and many are even helpful. They can help you digest food and kill off other harmful forms of bacteria that try to invade your body. But even the helpful ones can hurt you if they grow where they’re not supposed to.
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
Living, single-celled organisms that can reproduce on their own cause bacterial infections. Only a few types of bacteria cause illness in people.
An organism that’s not made up of cells causes viral infections. Viruses always need to infect humans or other living things to create more copies of itself.
Antibiotics can treat most bacterial infections, but only a few viral infections have medications that treat them.
Bacteria can cause many types of infections, depending on how you’re exposed and what part of your body it infects. Some common types of bacterial infections include:
Common bacterial infections include:
There are many bacterial infections that aren’t usually serious or can be treated easily with antibiotics. Impetigo and boils are examples. However, any bacterial infection that gets deep into your body, like in your blood, heart, lungs or brain, can be life-threatening.
Bacterial infections can spread through droplets or dust in the air, direct or indirect contact, a vector (like a tick or mosquito) or contaminated food or water (vehicular).
You can get bacterial infections through the air from contaminated dust or droplets of water or mucus (like phlegm or snot). Legionnaires’ disease, pertussis (whooping cough), tuberculosis, meningococcal disease and strep throat spread this way.
You can get bacterial infections from direct contact with infected skin or mucous membranes, or from indirect contact with contaminated surfaces. Bacterial diseases you get by contact include skin infections and some sexually transmitted infections (STIs) like gonorrhea and chlamydia.
While it sounds like something you get from your car, “vehicular” usually means you get sick from water or food (the “vehicle” of transmission). You can get gut (gastrointestinal) infections from E. coli, Campylobacter and Salmonella bacteria in contaminated food or water.
Anyone can get a bacterial disease, and most of us will at some point in our lives. You’re at higher risk for getting an infection if you have:
Bacteria can hurt your body either when they reproduce or by releasing poisons (toxins) that damage your cells. Infections that only affect the surface of your skin or mucous membranes (like your throat or intestines) aren’t usually serious, but sometimes, bacteria can spread in your body and cause life-threatening illnesses. If bacteria gets into your blood, it can cause sepsis, a reaction to the infection that causes organ damage, which is sometimes fatal.
Symptoms of bacterial infections vary depending on where in your body is infected. The main symptom is often fever, except skin infections, which usually cause redness or pain on your skin. Common symptoms of bacterial infections include:
Additional symptoms can include:
Many kinds of bacteria cause infections. You usually get bacterial infections when bacteria get into your body through your mouth, your nose, your eyes or a cut in your skin. Sometimes, bacteria that normally live on your skin or in your body get into places they’re not supposed to (like through an injury) and reproduce.
Common ways you can get bacterial infections include:
Yes, many bacterial infections are contagious from person to person, including pertussis, tuberculosis, strep throat, meningococcal disease, bacterial STIs and MRSA. Infections you get from food, mosquitos or ticks are usually not contagious.
A healthcare provider diagnoses a bacterial infection by listening to your symptoms, doing an examination (listening to your heart and lungs, feeling your abdomen, looking at your skin) and taking samples to test for bacteria.
Your provider might send body fluid or tissue samples to a lab to look for signs of an infection (antibodies or antigens). A lab technician might also try to grow bacteria from your samples. Types of samples they might take include:
Not all bacterial infections need to be treated — some go away on their own. When you do need treatment, healthcare providers use antibiotics. Depending on where your infection is and how serious it is, antibiotics can be prescribed as:
Sometimes, certain antibiotics stop working and don’t kill or slow down bacteria (antibiotic resistance). Because of this, doctors and nurse practitioners are careful about when and how they prescribe antibiotics. They only prescribe them if they think they’ll help you. It’s important for you to take any medication as prescribed for the full course, even if you start to feel better.
Ways to reduce your risk of various types of bacterial infections include:
What to expect depends on what kind of bacterial infection you have. Less serious bacterial infections are treatable with medication at home. Others require a hospital stay and can cause lasting damage. Bacterial infections in your internal organs or blood can be life-threatening.
Bacterial infections inside of your body can cause serious complications. The most serious complication is sepsis, a life-threatening reaction to an infection that causes organ damage. Sepsis can be fatal.
If you’re prescribed antibiotics for a bacterial infection, you’ll usually have to take them for a week or two, though you’ll probably feel better sooner. Take all of your medication as prescribed, otherwise, you might not get rid of all of the bacteria.
Antibiotics usually cure bacterial infections. They sometimes go away on their own or can be treated without antibiotics, but it’s always best to check with a healthcare provider for the best way to treat them.
Contact a healthcare provider if you have symptoms of a bacterial infection, especially if you’ve had them for more than a couple of days. Make sure to follow up with your provider if you’ve been treating an infection and your symptoms aren’t getting better or are getting worse.
Go to the nearest ER or seek immediate medical attention if you have signs of a serious infection, including:
A note from Cleveland Clinic
Bacteria live all around us — millions even live on or in us. They help us digest nutrients, protect us from harmful invaders and even help in making delicious foods. But, like puppies in a shoe factory, they can cause a lot of damage if they’re somewhere they’re not supposed to be. Bacterial infections can be a temporary nuisance, but they can also turn into a life-threatening situation. Always check with a healthcare provider to make sure you know the best way to manage a bacterial disease.
Last reviewed by a Cleveland Clinic medical professional on 09/20/2022.
Learn more about our editorial process.