Pathogens, types of infection, laboratory tests and prevention terms, defined in plain language for pre-med and nursing students, medical assistants and healthcare professionals.
Last updated: October 26, 2026
Infectious diseases is the specialty that deals with illnesses caused by microorganisms. Its vocabulary describes the agents responsible, how infections spread, how they are detected and how they are treated or prevented. Knowing these terms makes reports, lab results and clinical notes much easier to read.
| Term | Definition |
|---|---|
| Pathogen | A microorganism capable of causing disease in a host. |
| Bacterium | A single-celled microorganism without a nucleus, some of which cause infections that antibiotics can treat. |
| Virus | A very small infectious agent that can only multiply inside the cells of a host. |
| Fungus | A microorganism such as a yeast or a mold that can cause infections of the skin, mucous membranes or deeper tissues. |
| Parasite | An organism that lives on or inside a host and draws nourishment from it, sometimes causing disease. |
| Infection | The invasion and multiplication of a microorganism in the body, which may or may not cause symptoms. |
| Contagious | Describes a disease that can be passed directly or indirectly from one person to another. |
| Transmission | The way a pathogen passes from a source to a new host, for example through contact, droplets, blood or contaminated food. |
| Incubation period | The time between exposure to a pathogen and the appearance of the first symptoms. |
| Fever | A rise in body temperature above its normal range, often a sign that the body is fighting an infection. |
| Bacteremia | The presence of bacteria in the bloodstream. |
| Sepsis | A life-threatening reaction of the body to an infection, which can damage organs. |
| Abscess | A localized collection of pus enclosed in a tissue, usually caused by a bacterial infection. |
| Pneumonia | An infection of the lung tissue, often causing cough, fever and difficulty breathing. |
| Cellulitis | A bacterial infection of the deeper layers of the skin and the tissue just beneath it. |
| Meningitis | Inflammation of the membranes surrounding the brain and spinal cord, often caused by an infection. |
| Antibiotic | A medication that kills bacteria or stops them from multiplying; it is not effective against viruses. |
| Antiviral | A medication that targets a virus and limits its ability to multiply. |
| Antibiotic resistance | The ability of bacteria to survive the action of an antibiotic that used to be effective against them. |
| Culture | A laboratory test in which a sample is placed in a favorable medium to let microorganisms grow so they can be identified. |
| Antibiogram | A laboratory report showing which antibiotics a given bacterium is sensitive or resistant to. |
| Serology | A laboratory approach that looks for antibodies or antigens in the blood to reveal contact with a pathogen. |
| Vaccine | A preparation that trains the immune system to recognize a pathogen so that the body can respond quickly if exposed. |
| Isolation | A precaution that separates an infected person from others in order to limit the spread of a pathogen. |
| Asepsis | The set of measures used to prevent microorganisms from reaching a patient, a wound or a sterile site. |
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Start learning free →Infectious diseases vocabulary names the microorganisms that cause illness, the way they spread, the tests that detect them and the treatments that fight them. It is essential for reading lab results, infection-control notes and clinical reports.
The vocabulary of infectious diseases helps you understand lab reports, clinical notes and prevention guidance. It lets you tell apart a pathogen, an infection and a contagious disease, and follow how a diagnosis is confirmed and how spread is limited.
Yes. This vocabulary is core to US health programs — nursing school and NCLEX prep, pre-med, and medical assistant training. MediLearn lets you drill these terms with quizzes and flashcards using spaced repetition.
A microorganism such as a yeast or a mold that can cause infections of the skin, mucous membranes or deeper tissues.
A localized collection of pus enclosed in a tissue, usually caused by a bacterial infection.
A laboratory report showing which antibiotics a given bacterium is sensitive or resistant to.