Glossary of Terms

For clarification on all the terminology surrounding coronavirus, please review the glossary below:

Active monitoring:

means that the state or local public health authority assumes responsibility for establishing regular communication with potentially exposed people to assess for the presence of fever, cough, or difficulty breathing. For people with high-risk exposures, CDC recommends this communication occurs at least once each day. The mode of communication can be determined by the state or local public health authority and may include telephone calls or any electronic or internet-based means of communication.


A person who is asymptomatic is infected with SARS-COV-2 but never develops any symptoms of the infection. Researchers are working to determine how many people who get infected fit into this category — current estimates fall “anywhere between 6% and 41%,” a World Health Organization official said June 9. “Asymptomatic” is sometimes used to describe anyone who shows no symptoms at the time of testing positive for the virus but some of these individuals may actually be “presymptomatic” and will develop symptoms over the next few days.

Asymptomatic/presymptomatic spread:

When an infected person who has no symptoms of the disease transmits the novel coronavirus to someone else. It’s not clear how frequently people with no symptoms are spreading the virus, but researchers have documented spread from both asymptomatic and presymptomatic cases. That is the main reason many health departments recommend mask-wearing in shared spaces — to prevent the spread of the novel coronavirus, particularly from people who may not know they have it.

Close contact:

is defined as in CDC’s Interim Guidance for Healthcare Professionals.

Contact tracing:

Identifying people who may have come into contact with a person infected with a disease.

Congregate settings:

are public places where close contact with others may occur. Congregate settings include settings such as shopping centers, movie theaters, stadiums, workplaces, and schools and other classroom settings.

Controlled travel:

involves exclusion from long-distance commercial conveyances (e.g., aircraft, ship, train, bus). For people subject to active monitoring, any long-distance travel should be coordinated with public health authorities to ensure uninterrupted monitoring. Air travel is not allowed by commercial flight but may occur via approved noncommercial air transport. CDC may use public health orders or federal public health travel restrictions to enforce controlled travel. CDC also has the authority to issue travel permits to define the conditions of interstate travel within the United States for people under certain public health orders or if other conditions are met.

Droplet :

The spray produced by sneezing, coughing or even talking. Droplets can spread disease when an infected person coughs or sneezes — and the spray lands on a nearby person’s mouth, nose or eyes. It can also spread when a person touches a body part or a surface with infected droplets, then touches their face.


A sudden increase in the number of cases of a disease in a particular geographic area beyond the number health officials typically expect. An increase in a relatively small geographic area or among a small group of people may be called an “outbreak.” The difference between an outbreak, an epidemic and a pandemic is subjective and depends on the opinions of scientists and health officials.

Incubation period:

The period between exposure to an infection and the appearance of the first symptoms. CDC believes at this time that symptoms of 2019-nCoV may appear in as few as 2 days or as long as 14 after exposure. However, the exact incubation period is still unknown.


 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 to prevent spread of the communicable disease. Isolation for public health purposes may be voluntary or compelled by federal, state, or local public health order.


“An epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people,” according to A Dictionary of Epidemiology. The World Health Organization declared COVID-19 a global pandemic on March 11, 2020, describing it as “the first pandemic caused by a coronavirus.”

Person-to-person contact:

 How a disease might spread from one person to another. This can happen in many ways — by kissing, touching, having sex, exchanging bodily fluids, sneezing or coughing


How to avoid being exposed. Currently, there is no vaccine for 2019-nCoV. Everyday preventive actions will help prevent the spread of respiratory viruses, including:

  • Wash your hands often with soap and water for at least 20 seconds.
  • Avoid touching your eyes, nose, and mouth with unwashed hands
  • Avoid close contact with people who are sick
  • Stay home when you are sick.
  • Cover your cough or sneeze with a tissue, then throw the tissue in the trash.
  • Clean and disinfect frequently touched objects and surfaces.
Public health orders:

 are legally enforceable directives issued under the authority of a relevant federal, state, or local entity that, when applied to a person or group, may place restrictions on the activities undertaken by that person or group, potentially including movement restrictions or a requirement for monitoring by a public health authority, for the purposes of protecting the public’s health. Federal, state, or local public health orders may be issued to enforce isolation, quarantine or conditional release. The list of quarantinable communicable diseases for which federal public health orders are authorized is defined by Executive Order and includes “severe acute respiratory syndromes.” COVID-19 meets the definition for “severe acute respiratory syndromes” as set forth in Executive Order 13295, as amended by Executive Order 13375 and 13674, and, therefore, is a federally quarantinable communicable disease.


in general means the separation of a person or group of people reasonably believed to have been exposed to a communicable disease but not yet symptomatic, from others who have not been so exposed, to prevent the possible spread of the communicable disease.

Rate of Transmission:

The average number of people each coronavirus carrier goes on to infect — officially called the “effective reproductive number.” If each subsequent generation of new infections decreases (if RT <1), the virus eventually disappears. An area’s transmission rate depends on local policies and how people behave. “We can think of transmission risk with a simple phrase: time, space, people, place,” Dr. William Miller, an epidemiologist at Ohio State University, told NPR. The more time a person spends in close spatial proximity to infected people, the higher the likelihood that the virus will spread. Interacting with more people raises the risk, and indoor places are riskier than the outdoors. RT can decrease in areas where many people acquire immunity to the virus, because the virus then runs out of new people to infect. (A related term, R0 — pronounced “r nought” — is the average rate of transmission in a population where no one has previously been affected.)

Social distancing:

means remaining out of congregate settings, avoiding local public transportation (e.g., bus, subway, taxi, ride share), and maintaining distance (approximately 6 feet or 2 meters) from others. If social distancing is recommended, presence in congregate settings or use of local public transportation should only occur with approval of local or state health authorities.


means people should monitor themselves for fever by taking their temperatures twice a day and remain alert for cough or difficulty breathing. Anyone on self-monitoring should be provided a plan for whom to contact if they develop fever, cough, or difficulty breathing during the self-monitoring period to determine whether medical evaluation is needed.

Self-monitoring with delegated supervision:

means, for certain occupational groups (e.g., some healthcare or laboratory personnel, airline crew members), self-monitoring with oversight by the appropriate occupational health or infection control program in coordination with the health department of jurisdiction. The occupational health or infection control personnel for the employing organization should establish points of contact between the organization, the self-monitoring personnel, and the local or state health departments with jurisdiction for the location where self-monitoring personnel will be during the self-monitoring period. This communication should result in agreement on a plan for medical evaluation of personnel who develop fever, cough, or difficulty breathing during the self-monitoring period. The plan should include instructions for notifying occupational health and the local public health authority, and transportation arrangements to a pre-designated hospital, if medically necessary, with advance notice if fever, cough, or difficulty breathing occur. The supervising organization should remain in contact with personnel through the self-monitoring period to oversee self-monitoring activities.

Self-monitoring with public health supervision:

 means public health authorities assume the responsibility for oversight of self-monitoring for certain groups of people. CDC recommends that health departments establish initial communication with these people, provide a plan for self-monitoring and clear instructions for notifying the health department before the person seeks health care if they develop fever, cough, or difficulty breathing, and as resources allow, check in intermittently with these people over the course of the self-monitoring period. If travelers for whom public health supervision is recommended are identified at a US port of entry, CDC will notify state and territorial health departments with jurisdiction for the travelers’ final destinations.


 means people should remain alert for subjective fever, cough, or difficulty breathing. If they feel feverish or develop cough or difficulty breathing during the self-observation period, they should take their temperature, limit contact with others, and seek health advice by telephone from a healthcare provider or their local health department to determine whether medical evaluation is needed.

Superspreading event:

When a person infected with a pathogen passes it on to an unusually high number of people. With COVID-19, large case clusters have resulted from business conferenceschoir practices, funerals, family gatherings and cruises, among other settings. Virologists who researched superspreading events during the MERS outbreak say there are several possible reasons why these events emerge. Sometimes the virus may mutate to become more contagious. Or some people just exhale more virus from their lungs.

Symptoms compatible with COVID-19 infection:

for the purpose of these recommendations, include subjective or measured fever, cough, or difficulty breathing.


How a virus gets from one individual to the next. In the case of SARS-COV-2, researchers think the virus is primarily spread via the respiratory route, through close contact with an infected person, whose virus-laden droplets are expelled from the nose or mouth and find their way into the eyes, noses and mouths of others. Other possible routes of transmission, currently under investigation, include touching virus-contaminated surfaces and then introducing those germs to one’s eyes, nose or mouth; or breathing in clouds of tiny “aerosolized” virus particles that may be traveling on air currents.


None. There is no specific antiviral treatment currently recommended for 2019- nCoV infection. People infected with 2019-nCoV should receive supportive care to help relieve symptoms. For severe cases, treatment should include care to support vital organ functions.

*These terms were adopted from:

Centers for Disease Control and Prevention & National Public Radio

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