English for Infectious Diseases: Essential Vocabulary & Phrases

"airborne transmission"

The spread of infection through tiny infectious particles (aerosols) suspended in the air that can travel long distances.

"Measles spreads by airborne transmission, which is why isolation in negative-pressure rooms is required."

"fomite"

An inanimate object or surface that can carry and transfer infectious agents from one person to another.

"Doorknobs and shared keyboards act as fomites during norovirus outbreaks in healthcare settings."

"zoonotic"

Describing a disease or infection that can be transmitted between animals and humans.

"Rabies and avian influenza are zoonotic diseases that require careful surveillance at the animal–human interface."

"vector-borne"

Transmitted to humans through the bite of an infected arthropod such as a mosquito, tick, or flea.

"Malaria is a vector-borne disease carried by Anopheles mosquitoes in tropical and subtropical regions."

"incubation period"

The time between exposure to an infectious agent and the first appearance of symptoms.

"COVID-19 has an incubation period of two to fourteen days, complicating contact tracing efforts."

"index case"

The first identified case of a disease in a group or population, from which the outbreak is traced.

"Epidemiologists identified the index case at the seafood market before mapping the chain of transmission."

"herd immunity"

Indirect protection that occurs when a sufficient proportion of a population has become immune, limiting further spread.

"Vaccination campaigns aim to achieve herd immunity and protect those who cannot be vaccinated."

"R-naught (R₀)"

The basic reproduction number; the average number of people one infectious person will infect in a fully susceptible population.

"An R₀ greater than one means the outbreak will grow, while an R₀ below one indicates it will decline."

"pathogen"

A microorganism — such as a bacterium, virus, fungus, or parasite — capable of causing disease in a host.

"The laboratory identified the pathogen as Staphylococcus aureus, guiding the antibiotic selection."

"virulence"

The degree of pathogenicity of a microorganism; how severely it can cause disease in a host.

"The new strain showed increased virulence compared to previous isolates, alarming public health officials."

"gram-positive"

Bacteria that retain the crystal violet stain in the Gram staining technique, indicating a thick peptidoglycan cell wall.

"Streptococcus pneumoniae is a gram-positive bacterium and a leading cause of bacterial pneumonia."

"gram-negative"

Bacteria that do not retain crystal violet stain and have a thin cell wall with an outer lipopolysaccharide membrane.

"Gram-negative organisms like E. coli can release endotoxins that trigger septic shock."

"obligate intracellular"

A microorganism that can only reproduce inside living host cells, such as viruses and certain bacteria like Chlamydia.

"Because they are obligate intracellular pathogens, viruses cannot be grown on standard bacterial culture media."

"spore-forming"

Describing bacteria capable of producing dormant, highly resistant spores that survive extreme environmental conditions.

"Clostridium difficile is spore-forming, making it highly resistant to standard disinfectants on hospital surfaces."

"antimicrobial resistance"

The ability of a microorganism to withstand the effects of an antimicrobial drug that previously could kill it.

"Growing antimicrobial resistance to last-resort antibiotics is a critical global public health threat."

"biofilm"

A structured community of microorganisms attached to a surface and enclosed in a self-produced matrix, highly resistant to antibiotics.

"Catheter-associated infections often involve biofilm formation, significantly complicating treatment."

"polymerase chain reaction (PCR)"

A highly sensitive molecular technique that amplifies specific DNA or RNA sequences to detect the presence of a pathogen.

"Nasopharyngeal PCR testing became the gold standard for confirming SARS-CoV-2 infection."

"serology"

The laboratory analysis of blood serum to detect antibodies or antigens, indicating past or current infection or immunity.

"Serology confirmed prior dengue exposure, helping classify the patient's current episode as secondary infection."

"sensitivity"

The ability of a diagnostic test to correctly identify those who have the disease (true positive rate).

"High sensitivity is critical for screening tests to avoid missing active tuberculosis cases."

"specificity"

The ability of a test to correctly identify those who do not have the disease (true negative rate).

"A test with low specificity produces many false positives, which can trigger unnecessary treatment."

"culture and sensitivity"

A laboratory procedure that grows a microorganism from a sample and then tests which antimicrobials can inhibit its growth.

"Blood culture and sensitivity results guided the switch from broad-spectrum to targeted antibiotic therapy."

"point-of-care testing"

Diagnostic testing performed near or at the site of patient care, delivering rapid results without laboratory processing delays.

"Point-of-care testing for influenza allowed the clinician to prescribe oseltamivir within minutes of the visit."

"viral load"

A measurement of the amount of virus present in a given volume of body fluid, used to monitor infection progression and treatment response.

"Undetectable viral load in HIV patients indicates effective antiretroviral therapy."

"seroconversion"

The process by which antibodies against a specific pathogen become detectable in the blood following infection or vaccination.

"Seroconversion was confirmed four weeks after vaccination, indicating a successful immune response."

"broad-spectrum antibiotic"

An antibiotic effective against a wide range of both gram-positive and gram-negative bacteria.

"Pending culture results, a broad-spectrum antibiotic was started empirically to cover likely pathogens."

"antiretroviral therapy (ART)"

A combination of medications used to suppress HIV replication and prevent progression to AIDS.

"Adherence to antiretroviral therapy allows HIV-positive individuals to live long, healthy lives."

"prophylaxis"

Treatment given to prevent disease or infection rather than to treat an existing condition.

"Post-exposure prophylaxis with antiretrovirals must be started within 72 hours of HIV exposure."

"empirical therapy"

Treatment based on clinical judgment and likely pathogens before laboratory confirmation of the causative agent.

"Empirical therapy for community-acquired pneumonia was initiated while awaiting sputum culture results."

"de-escalation"

The practice of narrowing or stopping antimicrobial therapy once the causative pathogen and its susceptibilities are identified.

"De-escalation from vancomycin to oxacillin was appropriate after MSSA was confirmed on blood cultures."

"minimum inhibitory concentration (MIC)"

The lowest concentration of an antimicrobial that prevents visible growth of a microorganism in laboratory testing.

"The MIC breakpoint was used to classify the organism as susceptible or resistant to the chosen antibiotic."

"drug-drug interaction"

A situation where two or more drugs affect each other's activity, potentially increasing toxicity or reducing effectiveness.

"Rifampicin causes significant drug-drug interactions by inducing liver enzymes that metabolize many antiretrovirals."

"therapeutic drug monitoring"

Measuring drug levels in a patient's blood to ensure they remain within the therapeutic range and avoid toxicity.

"Therapeutic drug monitoring of vancomycin trough levels was performed every 48 hours in the ICU."

"epidemic"

A rapid increase in the number of cases of a disease in a specific population, area, or region above what is normally expected.

"The cholera epidemic spread rapidly through flood-affected communities lacking access to clean water."

"pandemic"

An epidemic that has spread across multiple countries or continents, typically affecting a large number of people globally.

"The WHO declared COVID-19 a pandemic in March 2020 as it spread across all world regions."

"endemic"

Describing a disease that is consistently present at a baseline level in a particular geographic area or population.

"Tuberculosis remains endemic in many low-income countries, requiring sustained public health investment."

"contact tracing"

The process of identifying and monitoring people who have been exposed to an infectious disease to prevent further transmission.

"Rapid contact tracing and quarantine were credited with breaking chains of transmission during the Ebola response."

"quarantine"

The restriction of movement or activities of people or animals that may have been exposed to a contagious disease but have not yet developed symptoms.

"A fourteen-day quarantine was mandated for all travelers returning from high-risk countries."

"isolation"

The separation of sick people with a contagious disease from those who are not infected, to prevent spread.

"Active tuberculosis cases were placed in respiratory isolation until sputum smears became negative."

"attack rate"

The proportion of people in a defined population who develop a disease following exposure to a pathogen during an outbreak.

"The high attack rate of 60% in the school canteen suggested a common food source for the outbreak."

"case fatality rate"

The proportion of people diagnosed with a specific disease who die from it within a given time period.

"The case fatality rate for Ebola varies between 25% and 90% depending on the strain and available care."

"standard precautions"

A set of infection control practices applied to all patients regardless of suspected or confirmed infection status.

"Standard precautions including hand hygiene and glove use are required for all patient contact."

"personal protective equipment (PPE)"

Protective clothing, helmets, gloves, face shields, goggles, facemasks, and respirators that protect the user from infection.

"Healthcare workers donned full PPE before entering the Ebola isolation unit."

"sterilization"

The complete elimination of all microbial life, including endospores, from instruments or surfaces using heat, radiation, or chemicals.

"Surgical instruments are subjected to steam sterilization in an autoclave before each procedure."

"disinfection"

The reduction of microbial contamination on inanimate objects to a safe level, which does not necessarily eliminate all spores.

"High-level disinfection of endoscopes is required to prevent transmission of blood-borne pathogens."

"immunization"

The process of making a person immune or resistant to an infectious disease, typically through vaccination.

"Routine childhood immunization has eliminated endemic polio from most countries worldwide."

"adjuvant"

A substance added to a vaccine to enhance the body's immune response to the antigen it contains.

"The use of an adjuvant in the influenza vaccine improved immunogenicity in elderly patients."

"hand hygiene"

The act of cleaning hands using soap and water or an alcohol-based hand rub to remove or kill pathogens and prevent transmission.

"WHO's five moments of hand hygiene framework has significantly reduced hospital-acquired infection rates."

"healthcare-associated infection (HAI)"

An infection acquired in a healthcare facility that was not present or incubating at the time of admission.

"Central line-associated bloodstream infections are a preventable form of healthcare-associated infection."