50 COVID-19 terms to know

Perhaps the first concept to understand is a virus. These microscopic organisms can live outside of a host, meaning they can be transmitted on surfaces or by air. One particular virus—SARS-CoV-2—is responsible for the disease known as COVID-19.

[Pictured: This digitally colorized, negative-stained transmission electron microscopic (TEM) image depicts a number of Influenza A virions.]

Severe acute respiratory syndrome, or SARS, is an illness caused by a coronavirus called SARS-CoV—importantly, a different coronavirus than the one that causes COVID-19. This virus originated in horseshoe bats, and the infectious disease known as SARS first appeared in humans in 2003. Though there is no vaccine for SARS, no outbreaks have occurred since 2003.

[Pictured: This illustration, created by the CDC, reveals ultrastructural morphology exhibited by coronaviruses.]

Like SARS, Middle East respiratory syndrome, or MERS, is also caused by a coronavirus. The specific virus—MERS-CoV—typically passes from animals to humans, and human-to-human transmission is rare. Most infections occur after contact with dromedary camels and nearly 80% of the worldwide cases were recorded in Saudi Arabia.

[Pictured: Produced by the National Institute of Allergy and Infectious Diseases, this highly magnified, digitally colorized scanning electron microscopic image revealed ultrastructural details at the site of interaction of numerous (yellow) MERS-CoV viral particles located on the surface of a (blue) Vero E6 cell.]

The novel coronavirus that causes COVID-19 is known as SARS-CoV-2. While this virus is similar to the coronaviruses that cause SARS and MERS, it remains distinct. Research into exactly how the virus operates and infects humans is still ongoing.

[Pictured: Visualization of COVID-19.]

Short for Coronavirus Disease 2019, COVID-19 is how most people refer to the infectious disease caused by SARS-CoV-2. Common symptoms include fever, cough, shortness of breath, fatigue, headache, sore throat, and nausea.

Antibodies play a crucial role in the immune system. The body releases these proteins into the bloodstream when it detects a particular virus or microbe that it deems a threat. Since antibodies develop after a person is exposed to a virus, scientists believe they may offer some protection from the same virus in the future, though it’s unclear to what degree COVID-19 antibodies can protect against future illness.

[Pictured: Computer illustration of influenza viruses coated with antibodies (white); antibodies bind to specific antigens.]

Antigens are proteins on a virus or germ that our immune system labels a threat, triggering an antibody response. Though testing for the presence of antigens can be a useful way to diagnose infectious diseases, scientists have not yet been able to find a unique protein target for COVID-19.

[Pictured: A chimeric antigen receptor molecule (light blue) binds to CD19 molecules (magenta) on a leukemia cell, activating a tyrosin kinase (red). The final result is the apoptosis of the cancer cell.]

Polymerase chain reaction tests, or PCR tests, reveal whether or not a patient currently has a disease such as COVID-19. These tests search for the presence of the virus in the nose, throat, or respiratory tract.

Unlike PCR tests, serology tests, also known as antibody tests, check for the presence of antibodies in the bloodstream to determine whether or not a patient has had an infection in the past. Scientists think antibody tests may eventually determine whether or not a person will have immunity to COVID-19, but don’t yet know the level of antibodies needed to confer immunity.

Antigen tests offer similar info to molecular tests, and within as little as 15 minutes following a nasal or throat swab. Antigen tests, which detect small pieces of the novel coronavirus that trigger immune system response, are less sensitive than PCR tests: If a patient has COVID-19 symptoms but a negative antigen test result, it is recommended they get a PCR test to be certain they don't have the virus. However, when it comes to a positive test result, antigen tests are highly accurate. This test is less expensive and complex, and faster than the other two types of approved diagnostic tests (molecular and PCR), so it can be useful in testing the masses; some experts predict that these tests may be widely available by this winter.

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A false positive is a conclusion that something is true when it actually isn’t. During the current pandemic, anecdotes of false negatives and false positives have popped up in the news, indicating that the PCR tests aren’t perhaps as reliable as scientists might hope.

Receiving a COVID-19 test with a false negative result means the test results indicate the patient does not have the virus when in fact they do. If a patient with COVID-19 symptoms has a negative antigen test result, but a positive PCR test, the antigen test may have delivered a false negative.

This branch of medical science has received a lot of buzz during the COVID-19 pandemic. Epidemiology refers to the scientific study of the causes of health outcomes of the population at large, including environmental factors, infectious diseases, injuries, and natural disasters.

Data scientists use mathematical models to calculate everything from cattle growth in a region to planetary motion, so why not use it to estimate the spread of COVID-19? Though several mathematical models for the pandemic—also known as disease models—exist, they vary wildly because scientists don’t have clear data on how many people have been infected, the infection rate, or the fatality rate.

One acronym that's been seen all over the news is WHO, which stands for the World Health Organization. This international organization seeks to build a healthier global future and fight diseases throughout the world with the help of its 194 member states.

Another acronym dominating the news cycle in the United States is the CDC, or Centers for Disease Control and Prevention. This government agency has led the COVID-19 response in the United States by advising the highest levels of government, publishing consumer guides to social distancing and other hot topics, collecting data on the outbreak within the United States, and more.

[Pictured: The David J. Sencer CDC Museum located on the Edward R. Roybal campus in Atlanta, Georgia.]

The Department of Health and Human Services (HHS) is the overarching branch of the federal government focused on health functions as the parent organization for the CDC and National Institutes of Health (NIH). The HHS will be taking an “America First” approach to distributing the future vaccine, according to Sept. 2 statements by senior HHS official Garrett Grigsby to the press.

Although the words “pandemic” and “epidemic” sound quite similar, there’s an important distinction. While an epidemic is an outbreak that spreads quickly and infects many people at once, a pandemic is a type of epidemic that affects an even greater number of people over a larger geographic area. As COVID-19 has spread worldwide, it’s been classified as a pandemic.

[Pictured: The World movie theater using its name to send a deeper-meaning message about the COVID-19 pandemic with its sign, "The world is temporarily closed."]

Much of the anxiety around COVID-19 centers on the fact that evidence suggests people can carry and transmit the disease while displaying few or no symptoms—in other words, they’re asymptomatic carriers. The realization that the virus can spread before you even realize you’re sick led to recommendations around social distancing, self-isolation, and even quarantine.

Also known as community transmission, community spread refers to the circulation of a disease within the population of a certain area with no clear connection to an infected patient. For example, a health care worker who contracted COVID-19 after caring for patients with the disease would not qualify as community spread, but a city dweller who tested positive without knowing anyone who had COVID-19 would.

Sneezing, coughing, and even speaking produces respiratory droplets that can carry germs and viruses, including COVID-19. When diseases spread through these droplets, it’s known as droplet transmission. According to the WHO, droplet transmission is one of the primary methods of contracting COVID-19.

Coffee cups, blankets, cardboard boxes, and countless other objects could all become fomites—or vehicles for the transmission of infectious diseases. Though fomites could potentially spread COVID-19, the CDC believes transmission from surfaces is less common than droplet spread.

Demand for bleach, isopropyl alcohol, and other disinfectants skyrocketed early in the pandemic, as these household disinfectants can kill the SARS-CoV-2 virus on surfaces. That said, disinfectants are not safe to ingest, inhale, or spray on the body.

Picture a line graph: A tall, triangular shape indicates numbers rising quickly, then falling equally fast, while a gradual, flatter curve indicates a slower rise, plateau, and fall. When this graph represents COVID-19 cases, the skyrocketing cases in the first scenario would overwhelm the health care system, but the more gradual increase in the second scenario would conserve medical resources. Flattening the curve refers to controlling the spread of COVID-19 to create the second, more preferable outcome.

This concept of herd immunity follows that if enough people get COVID-19, and the survivors build up antibodies that make them immune to future infections, the virus won't be able to find new hosts and will die out slowly. Some countries are banking on this idea as a way out of the current pandemic.

[Pictured: Family walking at Macau's Senado Square wearing protective face masks due to the COVID-19 outbreak.]

People whose immune systems aren’t able to fight off infections as well as their peers’ immune systems would be considered immunocompromised. Cancer treatment, organ transplants, history of smoking, and diabetes are just a handful of the conditions that can cause someone to become immunocompromised.

After a virus enters the human body, it incubates for a period of time before symptoms appear. For COVID-19, the incubation period is usually between two and 14 days, and patients can still be contagious during that time.

Although scientists don’t know exactly why, super-spreaders have the power to infect an unusually large amount of people with a disease. Thanks to super-spreaders, 20% of infected patients can drive up to 80% of new infections.

Viral shedding is the period of time when a virus is being emitted by a host after replicating. According to a German study published in March, COVID-19 patients can shed high amounts of the virus before they even realize they’re sick.

The basic reproduction number—also known as R0, pronounced R-naught—represents the average number of people who will catch a disease from an infected person. If it's greater than 1, the infection will likely continue to spread; when it falls below 1, the infection will likely start to fizzle out.

The test positivity rate indicates the percentage of people tested for a disease that actually test positive. For example, during the week of June 6, the national test positivity rate for COVID-19 was 6.3%, according to the CDC.

A person with two or more illnesses at the same time has comorbidity. Obesity, hypertension, and diabetes are three comorbidities that can contribute to worse health outcomes in COVID-19 patients.

Patients who require advanced respiratory support, among other care, might be transferred to the intensive care unit (ICU). COVID-19 patients who need to be put on a ventilator often end up in ICUs, and many stay longer than the average three or four days.

U.S. hospitals faced a massive shortage of ventilators in the spring of 2020. These are medical devices that help people breathe if they’re unable to do so on their own. About 25% of all critically ill COVID-19 patients will need a ventilator.

This experimental medical treatment uses plasma from a recovered COVID-19 patient to treat someone who is currently sick with the disease. Though researchers don't know how effective this therapy is yet, they hope it can help patients with severe symptoms fight the virus as well as help more moderate cases recover more quickly.

Personal protective equipment, or PPE, refers to the face masks, N95 respirators, face shields, gloves, gowns, and other coverings that health care workers use to prevent the spread of COVID-19. A shortage of PPE hamstrung hospitals in the spring of 2020, and the U.S. Food & Drug Administration (FDA) anticipates that the supply chain will continue to be stressed for the remainder of the pandemic.

Also known as an N95 mask, this form of PPE looks like a face mask that forms a tight seal around the nose and mouth. Not only does the material filter out 95% of the particles in the air, but the N95 respirator also requires a special 20-minute fit test to ensure it works properly.

Patient outcomes just refer to the end result of medical treatment on a patient, and this concept is used to evaluate the quality of medical care. A patient’s safety, satisfaction, and status help determine the patient outcome.

Clinical trials are a crucial step in the development of any medication—including a potential COVID-19 vaccine. Vaccine trials typically occur in three phases: a small group trial to assess safety and immune system response, a much larger randomized trial, and efficacy or safety testing with thousands of patients.

In a randomized trial, patients are randomly assigned into either an experiment group or a control group. The outcome being studied should be the only difference between the two groups.

Peer review is a crucial component of academic publishing. Scientific journals rely on academics and experts reviewing one another’s articles to both weed out errors and improve the strength of an article under consideration. However, peer review takes time—anywhere from four weeks to six months—and some experts say the public can’t afford to wait that long for crucial information about COVID-19.

Scholars and experts who aren’t willing to wait for their work to be peer reviewed often turn to preprint servers to make their manuscripts available right away. Also known as unrefereed preprints, these services publish work before it is peer reviewed or certified by a journal.

Another important part of the fight against COVID-19 is contact tracing. This process traces and monitors all of the people who had contact with an infected person to ensure everyone who was exposed quarantines. Effective contact tracing could slow the spread of the virus.

[Pictured: The CDC activated its Emergency Operations Center to coordinate with WHO, federal, state and local public health partners, and clinicians in response to COVID-19.]

When governors across the United States issued stay-at-home orders for their constituents, one category of worker was often given an exception: essential workers. This category includes health care professionals, grocery store employees, public transportation workers, and other employees whose jobs were deemed crucial to the community.

[Pictured: A bus driver for the public transit system, an essential worker during the COVID-19 pandemic.]

In epidemiology, the concept of excess deaths refers to the difference between the normal number of deaths and the reported number of deaths. Measuring the number of excess deaths is another way to estimate how many people have been killed by COVID-19.

[Pictured: A tally of deaths, confirmed cases, and other key metrics at one point during the COVID-19 pandemic.]

The FDA must provide official approval for a new drug or biologic before it can be marketed in interstate commerce. Simply put, FDA approval means the agency has decided that the potential benefits of a drug outweigh the known risks.

Commonly used to treat malaria, rheumatoid arthritis, and lupus, this drug came into the spotlight as a potential treatment for COVID-19 in March when the FDA granted an emergency authorization for its use during the pandemic. However, subsequent clinical trials found that hydroxychloroquine may not be effective after all, and the FDA revoked its authorization on June 15.

Though biotech company Gilead Sciences first began researching remdesivir as a potential treatment for hepatitis C in 2009, the drug recently rose to prominence for its possible use against COVID-19. Remdesivir has broad-spectrum antiviral activity, so experts think it could potentially improve recovery time for COVID-19 patients. Preliminary studies on the drug’s efficacy, however, have had mixed results.

A racial disparity refers to disproportionate differences among racial groups in regard to social constructs as seen in prison populations, health care, and employment rates in the U.S. (among others). During the pandemic, data show communities of color have been disproportionately affected by COVID-19. Black people are dying at a rate nearly twice as high as might be expected from their share of the U.S. population, according to the COVID Tracking Project. Additionally, the Navajo Nation has an infection rate per capita that’s higher than any U.S. state.

Known as "the nation's doctor," the surgeon general takes responsibility for the health of Americans across the country, issuing advisories and reports about the latest scientific information. Currently, Vice Adm. Jerome Adams, M.D. serves as the 20th Surgeon General of the United States.

[Pictured: U.S. Surgeon General Jerome Adams speaks as President Donald Trump and Vice President Mike Pence look on during the daily briefing of the White House Coronavirus Task Force in the James Brady Briefing Room April 10, 2020, at the White House.]