What does infection mean?
An infection is the invasion and multiplication of harmful microorganisms in or on the body, or the illness that results from this process. The term applies to infections caused by bacteria, viruses, fungi, and parasites, although not every communicable disease is technically an infection. In everyday use, it can also mean the transmission of a disease-causing organism from one person or place to another. The word is especially common in medical and public-health contexts, as in “prevent infection,” “an active infection,” and “risk of infection.” Its meaning can be narrower than that of “contagion,” which often focuses on the transmissible agent or the act of spreading disease, whereas “infection” emphasizes the process within the affected person. Knowing the distinction is useful when discussing symptoms, diagnosis, vaccination, antibiotics, and disease control.
nounThe invasion and multiplication of harmful microorganisms in or on the body, or the resulting condition of being affected by disease. It may also refer more broadly to the transmission of a disease-causing organism from one person or place to another.
- The invasion and multiplication of disease-causing microorganisms within the body.
- A condition or illness resulting from such an invasion.
- The transmission of a disease-causing organism from one person, place, or object to another.
"The doctor prescribed antibiotics after the bacterial infection spread from her throat to her sinuses."
"Good ventilation can reduce the risk of infection in crowded indoor spaces."
"The vaccine is designed to prevent infection without causing the disease itself."
The plural is used for separate cases of infection, different types of infection, or the occurrence of multiple infections.
"The hospital reported fewer respiratory infections after introducing mask policies."
An infection is a biological takeover: harmless residents of the body become an invading, multiplying population.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does infection come from?
The word comes from Latin infectio, a noun meaning “a tainting” or “infection,” derived from inficere, “to taint” or “infect.” That verb combines the prefix in- with facere, meaning “to make.” The English word appeared in the Middle English period and later acquired its established medical sense.
Related word forms
How infection is actually used
In medical use, infection usually denotes the presence and multiplication of pathogenic microorganisms in or on the body. The word is broad, encompassing bacterial, viral, fungal, and parasitic infections; it should not be used as a synonym for every communicable disease, since not every disease is caused by an infection.
Easily confused with infection
Infection names the invasion or condition within an affected person, while contagion more often emphasizes something transmissible that spreads disease.
Infection is the noun naming the process or resulting condition, whereas infect is the verb meaning to cause that condition.