Yesterday (March 11, 2020), the World Health Organization declared the coronavirus disease, also known as COVID-19, a pandemic. Let’s break down the terms for our own understanding and help keep our patients and the public informed.

Pandemic

Pandemic refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people (CDC, 2012). Most often, a pandemic results from a novel strain of influenza, and in general, evolves over time as influenza strains mutate. However, the 2009 H1N1 pandemic illustrated that a pandemic could occur suddenly, without warning (Rebman, 2020).

Epidemic (CDC, 2012)

Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in that area. Epidemics may result from recent increases in amount or virulence of an agent, recent introduction into a setting where it has not been before, an enhanced mode of transmission, change in the susceptibility of the host response, and/or factors that increase host exposure or involve introduction through new portals of entry.

• An outbreak refers to an epidemic in a more limited geographic area. 
• A cluster refers to an aggregation of cases grouped in place and time that are suspected to be greater than the number expected, even if the expected number may not be known. 

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COVID-19: Terminology and Preparedness

Social distancing (CDC, 2020a)

Social distancing refers to remaining out of congregate settings, avoiding mass gatherings, and maintaining a distance of about 6 feet or 2 meters from others.

Quarantine (Rebman, 2020)

Quarantine is the separation of people who are not yet symptomatic but have been exposed to a contagious person and are believed to be at risk of developing an infection. Exposed people are separated from others to rapidly identify onset of illness if it occurs and keep them away from susceptible people. Once a person in quarantine develops signs or symptoms of disease, it should be assumed that they are infected, and they would need to be isolated. Quarantine also means excluding healthy people from areas that are known or suspected of being contaminated or housing infected patients. Quarantines can be voluntary or enforced. In general, the length of quarantine equals the length of the incubation period for the disease to which the person was exposed.

Isolation (CDC, 2020a)

Isolation means the separation of a person or group of people known or reasonably believed to be infected with a communicable disease and potentially infectious from those who are not infected. Isolation may be voluntary or enforced by federal, state, or local public health order.

Transmission/spread (CDC, 2020b)

Transmission refers to the mechanism(s) by which an infectious agent spreads. At the time of this writing, we are still learning how COVID-19 spreads and to what extent we can expect. The current thought is that person to person transmission of COVID-19 is the main mode of transmission. People are thought to be most contagious when they are most symptomatic. Some spread might be possible before people show symptoms and it may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it and then touching their own mouth, nose, or possibly their eyes, but this is not thought to be the main way the virus spreads.

Incubation period (CDC, 2020b)

The incubation period is the time from exposure to the virus until the first symptoms develop.

What about specific terminology you may be hearing related to the virus itself?

Viruses, and the diseases they cause, are named differently. Think: human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency virus (AIDS).

Here are the basics related to COVID-19 (WHO, 2020):

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)
SARS-CoV-2 is the virus causing COVID-19. This virus name was determined by the International Committee on Taxonomy of Viruses (ICTV) on February 11, 2020 due to its genetic relation to the coronavirus responsible for the SARS outbreak of 2003.  

Coronavirus disease (COVID-19)
On February 11, 2020, the World Health Organization named this disease coronavirus disease, or COVID-19, in the International Classification of Diseases (ICD).
 

References:
Centers for Disease Control and Prevention (CDC). (2012). Principles of Epidemiology in Public Health Practice, Third Edition. Lesson 1: Introduction to Epidemiology. Retrieved from https://www.cdc.gov/csels/dsepd/ss1978/lesson1/section11.html

Centers for Disease Control and Prevention (CDC). (2020a). Interim US Guidance for Risk Assessment and Public Health Management of Persons with Potential Coronavirus Disease 2019 (COVID-19) Exposures: Geographic Risk and Contacts of Laboratory-confirmed Cases. Retrieved from https://www.cdc.gov/coronavirus/2019-ncov/php/risk-assessment.html

Centers for Disease Control and Prevention (CDC). (2020b). How COVID-19 Spreads. Retrieved from https://www.cdc.gov/coronavirus/2019-ncov/about/transmission.html

Rebman, A. (2020). Infectious Disease Disasters: Bioterrorism, Emerging Infections, and Pandemics. Association for Professionals in Infection Control & Epidemiology (APIC) Text Online.

World Health Organization (2020). Naming the coronavirus disease (COVID-19) and the virus that causes it. Retrieved from https://www.who.int/emergencies/diseases/novel-coronavirus-2019/technical-guidance/naming-the-coronavirus-disease-(covid-2019)-and-the-virus-that-causes-it