Coronavirus (COVID-19) glossary: What do these pandemic terms mean?

Last updated July 17, 2020

The novel coronavirus – also known as COVID-19 – has introduced many new terms to our vocabulary: from “community spread” to "contact tracing." But what exactly do these words mean?

What’s the difference between an “outbreak,” an “epidemic” and a “pandemic”? What about “self-isolation” and “self-quarantine”? And what does “flattening the curve” mean?

We spoke with our infectious diseases and infection control specialist Roy Chemaly, M.D. Here are the words he wants everyone to know.

Airborne: When a virus can be transmitted from person to person by the tiny particles of moisture released from the mouth or nose when speaking, breathing or singing. 

Asymptomatic: Not showing any signs of illness. The most common COVID-19 symptoms  are fever, cough, and shortness of breath, but you can still be contagious without showing any symptoms.

Cluster: Two or more people who shared the same space at the same time when they developed symptoms and who subsequently tested positive for COVID-19.

Community spread: Used when the source of someone’s coronavirus infection is unknown. In the case of COVID-19, this means it was not due to recent travel to a high-risk area, or exposure to someone with confirmed or suspected COVID-19.

Contact tracing: An attempt by public health officials to identify situations in which an infected person is transmitting the coronavirus, and then warn others who may have been exposed through that person. 

Contagious: Communicable, or able to be passed from one person to another. COVID-19 is thought to be spread primarily through direct contact with an infected individual, by inhaling the microscopic droplets sprayed into the air during a cough or sneeze, or by touching a contaminated surface and then touching one’s eyes, nose or mouth.

Coronavirus: A type of microscopic organism that causes illness in humans. “Corona” alludes to the tiny spikes found on the surface of the virus, which scientists thought resembled a crown, when seen through a microscope.

COVID-19: A shorthand way of referring to the novel COrona VIrus Disease, an upper respiratory infection that was first identified in 2019. The germ that causes it is formally known as SARS-CoV-2.

Epidemic: A cluster of outbreaks that have spread from one geographical area to others; also see related terms, “pandemic” and “outbreak.”

Exposure: Happens when you are within six feet of someone who is showing symptoms of COVID-19, for at least 15 minutes, when neither person is wearing a mask, and the infected person later tests positive for the coronavirus. It does not count as exposure if either or both individuals were wearing a mask.

Flattening the curve: An attempt to slow the spread of coronavirus and prevent a dramatic increase in the number of infected individuals. By practicing social distancing, avoiding unnecessary travel, and taking basic precautions, healthy individuals can help slow the spread of the disease — or “flatten the curve.”

Herd immunity: When enough people have developed immunity to a particular infectious disease that the risk of further community transmission is either eliminated or significantly reduced.

Incubation period: The amount of time it takes for an infected person to start showing symptoms of illness after exposure. In the case of coronavirus, the incubation period is thought to be between two days and two weeks, with the average being five days before symptoms start to appear.

mRNA: short for “messenger ribonucleic acid,” this is a chain of four distinct ribonucleic acid molecules linked together in a specific order. The order and length of mRNA provide the genetic instructions that tell our cells which proteins to make, including those needed for growth, energy production, and self-defense.

Mutation: Any change to the genetic code of an organism; a mutation can be “silent” (causing no discernable change to the organism) or it can alter the function, behavior or appearance of the organism.

Outbreak: A sudden increase in the number of cases of a particular disease in a relatively small geographical area. COVID-19 is thought to have originated in the Hubei Province in China. Also see related terms, “epidemic” and “pandemic.”

Pandemic: The worldwide spread of a new contagious disease that has infected a large number of people. The World Health Organization officially declared COVID-19 a pandemic on March 11, 2020. Also see related terms, “epidemic” and outbreak.”

Personal Protective Equipment (PPE): Equipment worn to minimize exposure to hazards that could cause workplace illness or injury.

Quarantine: The practice of isolating people who appear healthy, but may have been exposed to a contagious disease, such as COVID-19. Quarantines can be self-imposed or government mandated.

Screening: A basic series of questions posed by medical personnel to determine if someone should be tested for a particular disease or condition. In the case of coronavirus, screening may include taking your temperature, and questions about possible exposure to someone with confirmed or suspected COVID-19.

Self-isolation: The practice of separating someone who is sick from healthy individuals to prevent the spread of disease. Strategies include confining oneself to a single room/bathroom during the recovery period and not going out in public until the danger of transmission has passed. 

Self-quarantine: The practice of isolating yourself from others until it is considered safe to return to public life. In the case of COVID-19, people who suspect they might have been exposed to the virus should self-quarantine for 14 days.

Shelter-in-place: The definition of this term can vary, but in the COVID-19 context, it generally means staying home except to buy essentials such as food, gas or medicine, and minimizing contact with people outside of your immediate household.

Social distancing: The practice of staying at least six feet away from other people, avoiding crowds and gatherings, and limiting or cancelling all unnecessary travel to reduce the spread of disease.

State of emergency: A legal designation that allows civic leaders to request and obtain certain types of financial aid from the government, and take certain actions to protect the public.

Strain: a variant of an organism, such as a virus, that has one or more mutations. New strains of virus may be more contagious than the original, more likely to cause severe illness, or both.

Suspected COVID-19: Refers to a patient who is exhibiting COVID-19 symptoms and is currently awaiting test results.

Symptom: Any visible sign of illness that can indicate someone has been infected by a particular pathogen. Typical COVID-19 symptoms are fever, cough and shortness of breath.

Testing: The practice of using blood, urine, saliva, mucus or some other bodily fluid to determine if someone either has a specific condition or has been exposed to a particular infectious disease. In the case of COVID-19, patients must first undergo screening to determine if they need to be tested.

“It’s really important to learn and understand terms like these, especially when they’re related to a public health threat,” Chemaly says. “After all, if you don’t even know what ‘social distancing’ really means, how can you be expected to do it?”

Learn more about COVID-19 and precautions MD Anderson is taking.

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