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COVID-19 Glossary of Terms

The following COVID-19 glossary is an alphabetical list of terms with the definitions.

To download and view the COVID-19 Glossary of Terms, click here.



AESD: Adelanto Elementary School District

AESD Isolation Room: A space at the school for a student or staff member who may or may not have COVID-19 to wait until further instruction. Please note that having a student wait in an isolation room or a quarantine room is not indicative of the student's COVID-19 status.

CDPH: California Department of Public Health

Close Contact: Someone who was within 6 feet (for a cumulative total of 15 minutes or more over a 24-hour period) of a symptomatic or PCR confirmed COVID-19 positive individual. [CDPH]

Exposure Date: The date the confirmed COVID-19 positive individual had close contact with another individual. This will be the date used to determine the quarantine start date.

Isolation: Separates those infected with a contagious disease from people who are not infected. [CDPH]

Isolation Period: Isolation period will depend on whether the individual has symptoms or not. See Below:(return to school on day 11)

Symptomatic Individuals: Start date will be when the symptoms began and the end date will be after the individual meets the following three criteria:

  • At least 10 days have passed since symptom onset; AND
  • At least 24 hours have passed since resolution of fever without the use of fever-reducing medications; AND
  • Other symptoms have improved

Asymptomatic Individuals: Start date will be of the Date when the specimen was collected for the COVID-19 diagnostic test and the end date will be:

  • At least 10 days have passed since the date of the first positive COVID-19 diagnostic (return to school on day 11)

Infectious Period: You are considered to be contagious from 2 days before your first symptom(s) begin until you are done with self-isolation. If you had a positive COVID-19 test, but no symptoms, you are considered to be contagious from 2 days before your test date until 10 days after your positive test. [CDPH]

Quarantine: Restricts the movement of persons who were exposed to a contagious disease in case they become infected. Close contacts who were exposed to COVID-19 need to be quarantined, which means staying home for 10 days from their exposure date waiting to see if they get sick.

Quarantine Period: A 14-day duration where the close contact stays away and wait to see if they get sick, but per CDPH quarantine can be discontinued if it is after Day 10 from the date of last exposure without testing (return to school on day 11); OR

  • Quarantine can end after Day 7 if a diagnostic specimen is collected after Day 5 from the date of last exposure and tests negative.


  • Continue daily self-monitoring for symptoms through Day 14 from last known exposure; Follow all recommended non-pharmaceutical interventions (e.g., wearing a mask when around others, hand washing, avoiding crowds, and staying at least 6 feet from others) through Day 14 from last known exposure.

Modified Quarantine: Modified 10-day quarantine is for asymptomatic, unvaccinated students that are deemed close contacts may continue to attend in-person learning when:

  1. They continue to mask properly,
  2. Test twice weekly during the 10 day quarantine period,
  3. Refrain from all extracurricular activities in school (including sports) and from all extracurricular activities in the community setting.

*Modified quarantine is only applicable to students, not staff, and only if the exposure occurred in the school setting and if both the positive case and the close contact were wearing masks at the time of exposure.

Viral Load: the amount of virus present in the testing site (e.g. nasal cavity) at a given time.

Sensitivity: ability of a test to turn positive when an individual is in fact infected with SARS COV-2- the virus that causes COVID 19.

Specificity: ability of a test to be negative when an individual is not infected with SARS COV-2.

Stage of Infection: Sensitivity is also highly dependent on the stage of the infection. In general, after exposure and infection the amount of detectable virus in the body remains low for the first few days of infection then rises exponentially and then decreases gradually over a period of time.

Immune response of the infected individual: A person's individual immune response, their personal health characteristics can impact the time course of their infection which all influence the level of viral load at any time point.

Different labs: Each lab's tests have their own sensitivity and specificity levels. Labs with a higher level of sensitivity can detect lower viral loads of COVID-19 that might not get picked up by a test with a lower sensitivity level.

Different tests: Antigen tests and molecular tests have different abilities to detect viral loads thus impacting their sensitivities.

Sample collection and handling: Effective sample collection is dependent on different factors that can impact sample integrity including: collection technique and sealing of specimen, storage temperature, transportation, sample handling, and duration of time between sample collection and testing.



What is COVID-19?

A highly contagious respiratory disease caused by the COVID-19 virus. COVID-19 is thought to spread from person to person through droplets released when an infected person coughs, sneezes, or talks. It may also be spread by touching a surface with the virus on it and then touching one’s mouth, nose, or eyes, but this is less common.

What is a contact?

A person who has been exposed to COVID-19 virus through close contact with a Covid-19 positive individual or a contaminated surface/environment.

What is a case?

A person who has tested positive for COVID-19.

*A case may or may not experience COVID-19 symptoms. Or an individual who is showing signs and symptoms of COVID-19 and has not been tested.


Quarantine vs. Isolation

Quarantine Period

The separation of a person or group of people believed to have been exposed to COVID-19 virus but not yet symptomatic. Individuals are recommended to quarantine 10 days from the day they were exposed to someone with COVID-19 and monitor their symptoms for 14 days.

Isolation Period

Isolation is used to separate people infected with COVID-19 virus from those who are not infected. Individuals need to isolate 10 days from symptom onset or positive test collection date, and return to work or school on day 11 of their isolation period.

Infectious Period

For an individual who develops symptoms, the infectious period starts 2 days before they first develop symptoms and ends when 10 days have passed since symptoms first appeared.

For an individual who tests positive and asymptomatic, the infectious period starts 2 days before the specimen for their first positive COVID-19 test was collected and ends 10 days after.


Instructions for fully vaccinated individuals

Who is fully vaccinated?

In general, people are considered fully vaccinated: ± 2 weeks after their second dose in a 2-dose series, such as the Pfizer or Moderna vaccines, or 2 weeks after a single-dose vaccine, such as Johnson & Johnson's Janssen vaccine.

What is a Breakthrough case?

People who are fully vaccinated do NOT need to quarantine after contact with someone who had COVID-19 unless they have symptoms. However, fully vaccinated people should get tested 3-5 days after their exposure, even if they don’t have symptoms and wear a mask in public for 14 days following exposure or until their test result is negative.

Quarantine for fully-vaccinated individuals

A person who tests positive for COVID-19 ≥14 days after they have completed all recommended doses of a COVID-19 vaccine. Breakthrough cases are still recommended to follow a 10 day isolation.