Table of ContentsView AllTable of ContentsTypesGeneral SymptomsCauses and Risk FactorsDiagnosisTreatmentPrevention

Table of ContentsView All

View All

Table of Contents

Types

General Symptoms

Causes and Risk Factors

Diagnosis

Treatment

Prevention

Infection is a result of a microorganism (also called a pathogen) entering the body and causing harm. The organisms that cause infections are many and include things like viruses, bacteria, parasites, fungi, and prions.

There are many ways a person can contract an infection, including from another person, through contained foods or water, or a bug bite. Keep reading to learn about infections, including types, signs and symptoms, causes, and more.

Verywell / Theresa Chiechi

Types of Infection

How an infection spreads through the body will depend on the type of microorganism causing it. Sometimes, a microorganism will overwhelm the immune system’s ability to fight a pathogen off.

There are pathogens that have little effect on the immune system, while others produce inflammatory substances that trigger negative immune responses. There are also pathogens that might even be resistant to antibiotic therapy.

Viruses, bacteria, parasites, fungus, and prions are different types of pathogens that cause infections.

Viral Infections

Not all viruses destroy cells—some will change the function of a cell. Other viruses can lead to cancer because they force cells to uncontrollably replicate.

There are viruses that will stay with you for the rest of your life. These remain dormant within the body and then activate. Examples include herpes simplex virus or the varicella-zoster virus.

Treatment for a viral infection focuses on treating symptoms until the immune system clears out the infection. Some viral infections can be treated with antiviral drugs, including herpes and hepatitis C.

Bacterial Infections

There are bacteria in the body that can be helpful and not lead to disease. In fact, bacteria in the digestive tract can help with digestion and with keeping your body in balance.

Examples of bacterial infections include bacterial meningitis, pneumonia, tuberculosis, and food poisoning.

Bacterial infections are usually treated withantibiotics. These medications affect bacterial growth—either they stop growth, or they kill existing bacteria. There are different types of antibiotics so what you are prescribed will depend on the source of the infection.

You should always take antibiotics as prescribed. Make sure you finish an entire course even if you find you are feeling better after a few days. Not finishing antibiotics can keep the infection from clearing out and could lead to antibiotic resistance.

Parasitic Infections

Parasites are organisms that need to feed off other organisms to survive. Some parasites do not noticeably affect people, while others will grow, replicate, and invade organ systems.

The term “parasite” includes protozoa (parasites consisting of only one cell) and worms (parasites that are larger and have many cells).Examples ofparasitic infectionsare malaria, tapeworm infection, scabies, and pubic and head lice.

Parasitic infections are treated with specific drugs. This will differ based on the parasitic infection and how severe it is.

For example, malaria, which is a life-threatening condition that develops after an infected mosquito bites a person, is treated with anti-malarial drugs to kill the malaria parasite.Medications that treat malaria include chloroquine, Mepron (atovaquone), doxycycline, and intravenous (IV) artesunate.

Fungal Infections

Fungi live in different types of environments. The most commonly known fungi include yeast, mold, and edible fungi (i.e., mushrooms). Much like bacteria, there are fungi that exist on the skin and within the body.

A type of fungus—called mycosis—can cause infection. Examples includefungal nail infectionsand athlete’s foot.

Other types of fungal infection can occur in the membranes of the mouth and reproductive organs. These can also be life-threatening.

While hard to believe, fungi can be beneficial to humans. For example,penicillin, a widely-used antibiotic is made from a type of fungi mold calledPenicillium notatum.It is used to treat various bacterial infections.

Fungal infections are treated with antifungal medicines. The type of antifungal medicine your healthcare provider will prescribe will depend on the type of fungal infection causing your symptoms.

Prion Diseases

A protein called a prion might be responsible for causing an infectious disease.Prion diseasesinclude variably protease-sensitive prionopathy,fatal insomnia, Creutzfeldt-Jakob disease (CJD), andkuru. Fortunately, prion disease rare, without only about 300 cases reported in the United States.

Another type of CJD is related tomad cow disease.It can be transmitted when a person eats infected meat.

There are no cures for prion diseases. However, there are medicines to manage symptoms and slow down disease progression.

General Symptoms of Infection

The symptoms of infection will depend on the type of infection. General signs of infection might include:

Other more serious signs of infection that warrant calling your healthcare provider include:

You should also notify your practitioner if any infection symptoms worsen or don’t improve. Symptoms that recur or become chronic (lasting for a long time) should also be brought to your healthcare provider’s attention.

Complications

Most infections only cause minor problems. Some complications, like pneumonia or meningitis, can become life-threatening.

There are infections that have been linked to cancer.This includeshuman papillomavirus, which is linked to cervical cancer,Helicobacter pylorilinked to stomach cancer, and hepatitis B and C linked to liver cancer.

Infections can also be silent and will appear much later in life. Chickenpox is one such example. It might result in shingles in older adults who had chickenpox when they were younger.

There are many ways in which infections are acquired, including from direct and indirect contact, through contaminated food or water, or from a bug bite.

Direct Contact

Indirect Contact

Infections can be acquired through indirect contact. This is because many germs can linger on commonly touched surfaces, including doorknobs, faucets, and tables.

Indirect contact can be airborne through droplets from sneezing or coughing that can linger in the air for a short period.These droplets can make their way to a healthy person’s skin or can be inhaled into the respiratory passages and the lungs.

Contaminated Food or Water

You can become infected with an infectious disease through contaminated food or water.Escherichia coli(E.coli), for example, is a bacterium that can be found in foods like undercooked meat or unpasteurized milk.

Bug Bites

An infection can be acquired from an insect, such as a mosquito, flea, or tick. Mosquitoes can carry a malaria parasite or the West Nile virus.A deer tick carries bacteria that lead to Lyme disease.

Risk Factors

Anyone can catch an infection, regardless of the source. However, there are people who are more likely to get sick or have an increased risk for infection or infection complications.

People who are more susceptible to infections include:

If you have an increased risk for infection or complications of infection, you should get in touch with your healthcare provider if you experience symptoms of infection, regardless of the severity of those symptoms.

In cases where it is harder to make a diagnosis, your practitioner may request lab work. This might include taking samples of blood, urine, stool, sputum, or cerebrospinal fluid. These samples can help your healthcare provider determine what is causing symptoms and the type of organism causing symptoms.

Your practitioner might also request imaging, including an X-ray, computed tomography (CT) scan, or magnetic resonance imaging (MRI). Skin or tissue biopsies might be done to examine affected tissues.

Infections are treated according to their cause. The treatment for viral infections usually involves relieving symptoms until the immune system clears up the infection. However, some types of viral infections can be treated with anti-viral drugs.

Other medicines for treating infections are:

Talk to your healthcare provider about the best course of treatment for infection symptoms and to help you to get healthy again. You should also let your practitioner know if treatment doesn’t improve symptoms or makes them worse.

There is no single way to prevent infection. Harvard Medical School has recommendations that can you stay healthy and potentially avoid an infection.

Ways you can prevent infection include:

In addition to staying safe, eating a healthy diet and following an active lifestyle will help to keep your immune system strong enough to defend itself against infection.

12 Tips on How to Prevent Infectious Diseases

A Word From Verywell

Infections generally can be treated and managed at home. However, it is a good idea to contact your practitioner if you have symptoms of infection that do not appear to be improving, are getting worse, or become chronic. Your healthcare provider can prescribe additional medications to treat you or request additional testing to figure out if something else is causing your symptoms.

15 Sources

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Drexler M, Institute of Medicine (US).What you need to know about infectious disease. Washington (DC): National Academies Press (US). I, How Infection Works.

National Human Genome Research Institute.Bacteria.

Centers for Disease Control and Prevention.About parasites.

Cleveland Clinic.Malaria.

Centers for Disease Control and Prevention.Aspergillosis.

Harvard Medical School.Prion diseases.

Cleveland Clinic.Infectious diseases.

Cleveland Clinic.Shingles.

National Institutes of Health.What infections can affect pregnancy?

van Seventer JM, Hochberg NS.Principles of infectious diseases: transmission, diagnosis, prevention, and control.International Encyclopedia of Public Health. 2017;22-39. doi:10.1016/B978-0-12-803678-5.00516-6

Centers for Disease Control and Prevention.E. coli (Escherichia coli): Questions and answers.

Trident Health System.Ouch, what bit me? 10 common bug bites.

Harvard Medical School.If you are at higher risk. How to reduce risk of infection and what to do if you get sick.

Merz B. Harvard Medical School.How to prevent infections.

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