Antigen testA type of diagnostic test that checks to see if you're currently infected. The test looks for proteins (antigens) in a sample taken from your nose or throat. Antigen tests are faster than PCR tests, but they have a higher risk of false positives (meaning that they’re more likely to say you have the infection when you don’t). This may also be called a rapid test or rapid diagnostic test.

AsymptomaticNot showing any symptoms (signs of disease or illness). Some people without any symptoms still have and can spread the coronavirus. They’re asymptomatic, but contagious. Fever, cough, and shortness of breath are the main symptoms of COVID-19. Call your healthcare provider or clinic if you have any of the symptoms.

Case fatality rate (CFR)
An estimate of the risk of mortality from a contagious disease. The CFR is calculated by dividing the number of deaths caused by a disease by the number of cases of that disease in a given time period. 

Case investigation When a public agency interviews someone who has COVID-19 to determine where or by whom the individual may have gotten infected, understand symptoms, obtain demographics and underlying health conditions, and to identify close contacts.

The Centers for Disease Control (CDC)
The United States' federal health protection organization.

Clinically diagnosed When a person is diagnosed with a disease by their health care provider based on symptoms and risk factors, but they do not have a laboratory test to confirm the diagnosis.

Close contact
A person who may be at risk of a contagious disease because of their proximity or exposure to a known case. 

ClusterA grouping of disease cases in a geographic area during a set time period.

Communicable
Similar in meaning as "contagious." Used to describe diseases that can be spread or transmitted from one person to another.

Community spread
The spread of an illness within a particular location, like a neighborhood or town. During community spread, there's no clear source of contact or infection.

Confirmed case
Someone tested and confirmed to have COVID-19.

Congregate settings
Public places that can get crowded and where contact with infected people can happen. This includes places like malls, theaters, and grocery stores.

Contact tracing
The process of identifying, assessing, and managing people who have been exposed to a contagious disease to prevent onward transmission. 

Convalescent plasma therapyA treatment that involves taking blood from someone who has antibodies to a disease, separating out the clear liquid part (plasma), and then giving it to someone who is sick with the same illness. This technique has been used to treat many different diseases but is still considered experimental for treating COVID-19.

Cordon sanitaire
A measure preventing anyone from leaving a defined geographic area, such as a community, region, or country infected by a disease to stop the spread of the disease.

Coronavirus
A family of related viruses. Many of them cause respiratory illnesses. Coronaviruses cause COVID-19, SARS, MERS, and some strains of influenza, or flu. The coronavirus that causes COVID-19 is officially called SARS-CoV-2, which stands for severe acute respiratory syndrome coronavirus 2.

COVID-19
The name of the illness caused by the coronavirus SARS-CoV-2. COVID-19 stands for "coronavirus disease 2019.”

Direct transmissionThe transmission of a disease through direct physical contact, such as shaking hands or kissing, between an infected person and another, or when the spray produced by an infected person’s cough or sneeze reaches another’s nose, mouth or eyes.

Drive through testing
Individuals remain in their vehicles, and medical staff in protective gear come to administer the swab test and the swabs are sent to a laboratory for testing.

Droplet transmission/spread
A mode of transmission for a contagious disease that involves relatively large, short-range (less than 6 feet) respiratory droplets produced by sneezing, coughing, or talking. 

Emergency use authorizationA ruling put out by the FDA in an emergency, allowing medical professionals to use certain products before they have the agency’s full approval, clearance, or licensing.

Endemic
The baseline, or expected, level of the disease in the community—meaning it always exists, like the common cold and flu, which are usually at low, predictable rates.

Epidemic
A situation where more cases of disease than expected happen in a given area or to a group of people.

Epidemiology
The branch of medicine that studies how diseases happen and spread in communities of people. A person who studies epidemiology is called an epidemiologist.

Flattening the curveControlling the rate of new cases of COVID-19. Flattening the curve reduces the numbers of people needing healthcare at one time. This allows hospitals to treat patients throughout the pandemic.

Fomite
An inanimate object that can be the vehicle for transmission of an infectious agent (e.g., bedding, towels, or surgical instruments). There is evidence that coronavirus spreads via fomites although, this is a less common route of transmission.

Herd immunityWhen 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.

High-risk Those considered high-risk include older people or those with certain underlying health conditions. These include blood disorders, chronic kidney disease, chronic liver disease, a compromised immune system, late term or recent pregnancy, endocrine disorders, metabolic disorders, heart disease, lung disease, and neurological conditions. Check with your health care provider to see if you are considered high-risk.

Home isolation
Persons with COVID-19 who have symptoms or laboratory-confirmed COVID-19 who have been directed to stay at home until they are recovered. 

HydroxychloroquineA medication used to treat or prevent malaria. It’s now being used off-label to treat patients with COVID-19 based on very limited data showing that it has activity against SARS-CoV-2. Experts say it shouldn’t be used outside of clinical trials because its benefit isn’t clear and it could be toxic.

Immunity
Your body's ability to resist or fight off an infection. Your immune system is a network of cells throughout your body that help you avoid getting infected and help you get better when you are infected.

Immunocompromised
Also called immune-compromised or immunodeficient. This describes someone who has an immune system that can't resist or fight off infections as well as most people. This can be caused by several illnesses. Some treatments for illnesses can also cause someone to be immunocompromised.

Incubation period
The time it takes for someone with an infection to start showing symptoms. For COVID-19, symptoms appear 2-14 days after infection.

Indirect transmissionThe transmission of a disease through physical contact with contaminated surfaces, such as door handles or elevator buttons. There is evidence that coronavirus can survive on some hard surfaces for as long as three days

InfusionA procedure that puts a medicine, blood, or fluid directly into your veins through an IV or catheter over a period of time.

IsolationWhen a person who is showing symptoms of a disease separates themselves from other people to prevent spreading the disease to others. People who test positive for COVID-19 have to be isolated for at least 10 days after symptom onset and be fever free for 72 hours (without the use of medications) and have improvement in symptoms. People who are immunocompromised, hospitalized or health care workers may need to be isolated longer.

Lab-confirmed case When a person is diagnosed with a disease that is confirmed through having specimens (samples) tested in a laboratory.

Monitoring When an individual checks his/her temperature twice per day and watches for symptoms of COVID-19. Self-monitoring should be conducted by everyone but is especially important for travelers from high-risk areas and essential workers. Active monitoring is when a public health partner is calling a case or contact each day to check on his/her temperatures and symptoms.

Mortality rateThe number of deaths caused by a disease divided by the number of confirmed cases.

N95 respirator (face mask)
Personal protective equipment that is used to protect the wearer from airborne particles and from liquid contaminating the face.

Negative-pressure rooms
Rooms specifically designed for patients with contagious diseases that contain any circulating air in the room and prevent it from being released into any other part of the hospital.

Outbreak
A sudden increase of a specific illness in a small area.

PandemicAn epidemic that has spread over several countries or continents, impacting many people. Pandemics typically happen when a new virus spreads easily among people who—because the virus is new to them—have little or no pre-existing immunity to it. COVID-19, which was declared a pandemic by the WHO in early March, is the first pandemic known to be caused by the emergence of a new coronavirus. The CDC recognizes six stages to a pandemic. 

PCR testStands for polymerase chain reaction test. This is a diagnostic test that determines if you are infected by analyzing a sample to see if it contains genetic material from the virus.

PPE
PPE Stands for personal protective equipment. This includes masks, face shields, gloves, gowns and other coverings that healthcare workers use to prevent the spread of infection to themselves and other patients.

Person under investigation (PUI)
When a health provider suspects a person has the coronavirus. But, no test has confirmed the infection.

Presumptive positive case
When a person tests positive for the coronavirus, but the CDC hasn't confirmed the case.

Pre-symptomaticIf you’re pre-symptomatic, you have contracted the virus and may soon feel symptoms, but at the moment, you don't have any. It may be possible to spread COVID-19 to others during this phase.

QuarantineSometimes called "isolation." Quarantines keep people away from each other to prevent the spread of disease. Stay-at-home orders are a type of quarantine. Governments sometimes order quarantines to keep healthy people from exposure to infected people. They give rules to behavior and boundaries to movement.

R0 / reproductive rate
An epidemiologic metric used to describe the contagiousness or transmissibility of infectious agents, which is usually estimated with complex mathematical models developed using various sets of assumptions. It is an estimate of the average number of new cases of a disease that each case generates, at a given point in time.

Remdesivir
An antiviral drug made to treat Ebola (but never approved for that purpose), remdesivir is one of the medications being studied for its potential to treat COVID-19. The FDA granted it "emergency use authorization," which means some hospital-based health care providers are able to prescribe it to select patients.

Respiratory diseaseA disease that affects the lungs and other parts of the body involved with breathing. Coronavirus is a respiratory disease.

SARS-CoV-2Stands for severe acute respiratory syndrome coronavirus 2. SARS-CoV-2 is the specific strain of coronavirus that causes the COVID-19 disease.

ScreeningThis 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.

Self-isolationAlso called self-quarantine. Stricter than quarantine, self-isolation refers to staying in a contained area -- perhaps a single room in your home if you don't live alone -- because you have COVID-19 and are trying to avoid infecting others.

Serology testA test to see if you have antibodies in your blood that show that you were previously infected with the virus.

Shelter in place
An order for people to stay where they are and not leave for their own protection. A stay-at-home order is a kind of shelter-in-place order.

Social distancing
Also called physical distancing. It means putting space between yourself and other people at all times. The goal is to slow down how fast an infection spreads. Stay-at-home orders are a way that the government can enforce social distancing.

Super-spreaderOne person who, for unknown reasons, can infect an unusually large number of people. Infectious disease specialists say it is common for super-spreaders to play a large role in the transmission of viruses. In what's known as the 80/20 rule, 20% of infected patients may drive 80% of transmissions.

Suspected case A person who may have a disease because of their symptoms and risk factors based on current guidelines, but this person was not tested.

Swab testA type of diagnostic test that involves taking sample from the back of your nasal cavity so it can be analyzed in a lab to see if it contains the virus. Also called a viral test.

SymptomaticWhen a person shows signs of illness. For COVID-19, that includes cough, fever or shortness of breath.

TrialShort for clinical trial, this is when researchers study a medical test or treatment in a set group of people to make sure it’s safe and effective before giving it to the public.

Underlying conditionAn existing health problem that impairs an individual’s resistance to another disorder or disease. Among the underlying conditions that increase the risk of contracting a severe case of coronavirus are diabetes, heart disease, respiratory illnesses and immune system disorders.

VaccineA vaccine triggers the immune system to help it build immunity to a disease. The immune system already has the capacity to react to diseases by producing substances called antibodies that remain in the body to fight them in the future. With a vaccine, you don’t have to get the disease to develop immunity—the vaccine triggers the same process by providing the body with a tiny amount of a germ that has been weakened or killed, but small enough that it won’t make you sick. Vaccines are introduced to the body via injection, mouth, or a nasal spray.

Ventilator
A machine that supplies oxygen to a patient with severe lung issues. People with severe cases of COVID-19 can't provide enough oxygen to their body. Their lungs are too limited.

Viral loadAlso called a 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.

Viral shedding
The period of time after the virus has replicated in the host and is being emitted.

Viral testAlso called a diagnostic test, this checks to see if the active (live) virus is present in your body. In the case of COVID-19, this usually involves taking a sample from the back of your nasal cavity (swab test) so it can be analyzed in a lab to see if it contains genetic material from the virus.

VirusA tiny infectious organism made up of genetic material (DNA or RNA) wrapped in a protein coat. Viruses can't multiply on their own; they reproduce by invading living cells and taking control of them.

World Health Organization (WHO)
This United Nations organization monitors and protects public health around the world.

Zoonotic
This means that a disease was originally was detected in animal, but is now infecting people also.