Definition

Noun: An infection caused by a pathogen (such as a bacterium, virus, fungus, or parasite) that typically does not cause illness in healthy individuals but takes advantage of a weakened or compromised immune system to cause disease.

Usage

This term is used primarily in medical and healthcare contexts to describe infections that occur because the body's natural defenses are insufficient. It is a key concept in understanding diseases and conditions that impair immunity.

Examples

• Patients with advanced HIV/AIDS are highly susceptible to opportunistic infections like Pneumocystis pneumonia.
• The doctor explained that the fungal infection was an opportunistic infection, a direct result of the chemotherapy suppressing her immune system.
• Preventing opportunistic infections is a major focus of care for organ transplant recipients.

Advanced Usage

• "Opportunistic" as a Modifier: The adjective "opportunistic" is often used similarly in medical contexts to describe the nature of the pathogen or the disease process itself.
  • The virus is an opportunistic pathogen.
  • She developed an opportunistic pneumonia.

Variants and Related Words

• Opportunist (noun): An organism that causes an opportunistic infection.
• Opportunistic (adjective): Describing a pathogen that acts in this way, or a disease that arises in this manner (e.g., opportunistic disease).

Synonyms

• Secondary infection (in the context of pre-existing immune deficiency)
• OI (common medical abbreviation)

Notes on Different Meanings

The core meaning is strictly medical. In non-medical, general language, "opportunistic" describes a person who takes selfish advantage of situations, but the compound term "opportunistic infection" is not used in this figurative sense.

Noun

1. any infection caused by a microorganism that does not normally cause disease in humans; occurs in persons with abnormally functioning immune systems (as AIDS patients or transplant patients receiving immunosuppressive drugs)