When the majority of people in an area are immune to a specific infection, even the members of the population (herd) are protected simply by being around them. Anywhere from 50% to 90% of the population would have to have antibodies to COVID-19 in order for herd immunity to kick in.
The time between when a person is infected by a virus and when he or she notices symptoms of the disease. Estimates of the incubation period for COVID-19 range from 2-14 days, but usually is between 2 and 5 days.
On a larger scale, isolation involves keeping people with confirmed cases of a contagious disease separated from people who are not sick. If you have a confirmed case of COVID-19, for example, you may be put into isolation for public health purposes—it may be voluntary or compelled by federal, state, or local public health orders. The time period depends upon when symptoms first started and how rapidly symptoms improve.
A sudden increase or cluster of cases of a specific illness in a limited area or a facility.
Epidemic is the sudden, wide spread of a disease above what is usually expected.
Pandemic is when a disease spreads beyond national borders into other countries worldwide. An outbreak of severe pneumonia was noted in Wuhan, China related to a seafood market. As it spread rapidly in China it became an epidemic. As it spread to countries around the world, it became a pandemic.
This COVID-19 test detects genetic material of the virus using a lab technique called polymerase chain reaction (PCR). Also called a molecular test, a health care worker collects fluid from a nasal or throat swab or from saliva. PCR tests are very accurate when properly performed by a health care professional, but the rapid test can miss some cases.
Personal protective equipment (PPE)
Specialized clothing or equipment, worn for protection against infectious materials. In health care settings, PPE may include gloves, gowns, aprons, masks, respirators, goggles, and face shields. The CDC provides recommendations for when and what PPE should be used to prevent exposure to infectious diseases.
Positivity Rate or Percent of Tests Positive
There are two ways to calculate positivity rate:
Method 1: Divide (A) the number of people who have tested positive by (B) the number of people who have been tested. This method is used by Johns Hopkins and considered a more accurate picture of what is happening because duplicate tests for the same individuals are removed. It is not unusual for this to show a higher positivity rate than the method below.
Method 2: Divide (C) the number of positive tests by (D) the number of total tests. This method is used by Maryland Department of Health and does not remove duplicate tests on individuals during the time period.
With either method, a high volume of tests tends to lower the positivity rate.
Unlike isolation, quarantine involves separating and restricting the movements of people who were exposed to a contagious disease to see if they become sick. The government may impose a quarantine on someone who was exposed to COVID-19 to avoid spread of the disease to others if they get sick.
Rapid Antigen Test
This COVID-19 test detects certain proteins in the virus. Using a nasal or throat swab to get a fluid sample, antigen tests can produce results in minutes. Because these tests are faster and less expensive than PCR tests, antigen tests may be more practical to use for large numbers of people. A positive antigen test result is considered very accurate, but there’s an increased chance of false-negative results — meaning it’s possible to be infected with the virus but have a negative result. Depending on the situation, the doctor may recommend a PCR test to confirm a negative antigen test result.
This is not the same as a coronavirus test. This step helps healthcare workers to decide if you actually need a coronavirus test. It’s a series of basic questions about your health condition and recent history. Screening may also include other common healthcare procedures, like taking your temperature.
A voluntary agreement, this means you are to remain at home and not go to work or school. You’ll be expected to limit your movements outside and monitor your health for 14 days after returning from travel to or arriving from a place known to have high numbers of COVID-19 infections.
Self-quarantining is designed to restrict the movement of healthy people who may have been exposed to someone who has tested positive for COVID-19. The CDC suggests staying at home for 14 days from the exposure.
Also called an antibody test, this checks to see if you have antibodies in your bloodstream that indicate you had been infected with the virus in the past.
Shelter in Place
A decree, usually from a government official, for people to stay in their homes with exceptions that include going out for essential needs, such as groceries, as well as outdoor activities like walking and biking in public spaces. People who work in critical services, like health care or law enforcement, or essential businesses, are usually excluded from these mandates.
Maintaining a distance of approximately 6 feet from others to stop or slow the spread of COVID-19.
When a person shows signs of illness. For COVID-19, that includes cough, fever or shortness of breath.
Also called viral dose, viral load refers to the amount of virus you are exposed to. Someone who is exposed to a relatively small amount of the coronavirus might not get any symptoms, while someone who is exposed to a large amount is more apt to get severe symptoms.