The COVID-19 Pandemic: A Glossary of Terms

The coronavirus crisis has introduced a lot of new words into our daily vocabulary — words such as pandemic and asymptomatic and acronyms like PPE and PUI. All can be found in the dictionary or on websites for the Centers for Disease Control and Prevention, the Occupational Safety and Health Administration, and the American Red Cross. But what do they mean in everyday life?

The University of Alabama at Birmingham’s (UAB) Bertha Hidalgo, Ph.D., associate professor in the School of Public Health’s Department of Epidemiology, has translated some of coronavirus’s most-used terminology to help citizens better understand how the disease spreads and what can be done to stop it.

Virus vs. bacteria vs. germs

How Merriam-Webster defines “virus”: submicroscopic infectious agents, usually regarded as nonliving extremely complex molecules, that typically contain a protein coat surrounding an RNA or DNA core of genetic material but no semipermeable membrane, that are capable of growth and multiplication only in living cells and that cause various significant diseases in humans, animals and plants.

How Merriam-Webster defines “bacteria”: single-celled prokaryotic microorganisms that typically live in soil, water, organic matter, or the bodies of plants and animals and that make their own food.

How Merriam-Webster defines “germs”: a small mass of living substance capable of developing into an organism or one of its parts.


What their role is in the COVID-19 pandemic:“Viruses and bacteria are types of germs,” Hidalgo said. “Bacteria are bigger than viruses and can live without a host, since they get their nutrients from their environments, and some are actually good for us, like the ones that keep our gut working well. Viruses are pretty simple, actually — they are just little balls of genetic material surrounded by a protein coating. They tend to be smaller than bacteria and need a host to live. The COVID-19 virus is surrounded by a greasy covering, which can be broken down by soap. That’s why handwashing is so important for combating the virus, because it breaks the covering apart.”

Epidemic vs. pandemic

How Merriam-Webster defines “epidemic”: an outbreak of disease that spreads quickly and affects many individuals at the same time.

How Merriam-Webster defines a “pandemic”: an outbreak of a disease that occurs over a wide geographic area and affects an exceptionally high proportion of the population.

What their role is in the COVID-19 pandemic

“An epidemic is the sudden, fast spread of a disease,” Hidalgo said. “In the case of COVID-19, we first noticed an epidemic in Wuhan, China. As it spread outside Wuhan and beyond national borders into other countries, the epidemic became a pandemic — a widespread, worldwide spread of disease.


How Merriam-Webster defines “pandemic”: presenting no symptoms of disease.

What its role is in the COVID-19 pandemic: “This is an interesting term,” Hildago said. “It’s been associated with mild symptoms, when the word actually means to be ‘without’ symptoms. In the context of COVID-19, it means a period of time when someone has the virus and is able to infect others and make them sick, but may not feel any symptoms, or perhaps has symptoms so mild that they are missed entirely — things like infrequent sneezes, loss of smell or taste, or perhaps a light, dry cough.”


How Merriam-Webster defines “droplets”: a tiny drop, as of a liquid.

How Merriam-Webster defines “aerosols”: a suspension of fine solid or liquid particles in gas.

What their role is in the COVID-19 pandemic: Droplets are mucus or saliva that come out of the mouth and nose when you cough or sneeze. They contain the COVID-19 virus and can land on people or surfaces,” Hidalgo said. “Aerosols tend to be smaller than 0.0001 millimeters, which is really small — a ballpoint pen tip is about 0.1 millimeters. The New England Journal of Medicine says they can be suspended in the air for up to three hours. Droplets tend to be bigger, and because of that, they travel less distance when sneezed or coughed out and are more likely to fall on the ground than on a person or surface.”

From the moment a person gets infected, experts believe, there are four to five days before symptoms start.

Community spread

How Merriam-Webster defines “community spread”: the spread of a contagious disease to individuals in a particular geographic location who have no known contact with other infected individuals or who have not recently traveled to an area where the disease has any documented cases.

What its role is in the COVID-19 pandemic: “There are two types of coronavirus spread that happened in the United States: travel-related and community spread,” Hidalgo said. “The first means people who were infected traveled to the United States and infected others. ‘Community spread’ then happens when people who were infected by people who traveled begin infecting others, who then infect even more people. Eventually, so many people are infected within a community that it is difficult to determine who is infecting whom.”

Incubation period

How Merriam-Webster defines “incubation period”:  the length of time between the infection of an individual by a pathogen and the manifestation of the illness or disease it causes.

What its role is in the COVID-19 pandemic: “This is the period when someone has COVID-19 but isn’t showing signs or symptoms yet,” Hidalgo said. “For coronavirus, we think that, from the moment someone gets infected, there are four to five days prior to symptoms’ starting.”

Flattening the curve

How the Centers for Disease Control (CDC) defines “the curve”: a visual display of the onset of illness among cases associated with an outbreak.

What the role of “flattening the curve” is during the COVID-19 pandemic: “You want to spread out the rate of infection so as to not overwhelm our health care system and infrastructure,” Hidalgo said. “If everyone is out and about, it’s more likely that everyone will get sick at once. But if you’re able to spread out how many people get sick, over time, patients can get the treatment they need because hospitals and other resources will not be exhausted.”


How Merriam-Webster defines “apex” or “peak”: the highest or culminating point.

What its role is in the COVID-19 pandemic:  “This means the very top of the curve, usually the maximum number of cases, deaths and number of people recovered that have been counted or can be expected,” Hidalgo said.


How the CDC defines it: person under investigation (PUI).

What its role is in the COVID-19 pandemic: “These are people who likely have symptoms similar to those seen in coronavirus-positive patients,” Hildago said, “but might have tested negative for the virus.”


How the Occupational Safety and Health Administration (OSHA) defines it: personal protective equipment worn to minimize exposure to hazards that cause serious workplace injuries and illnesses.

What it role is in the COVID-19 pandemic: “This includes protective equipment like face masks, surgical gowns,  and gloves,” Hidalgo said.

Shelter-in-place vs. Stay-at-home

How the Red Cross defines “shelter-in-place”: Taking shelter in a a small, interior room, with no or few windows.

How Merriam-Webster defines “stay-at-home”: remaining in one’s residence, locality or country, especially remaining at home to tend to children and domestic duties while a spouse is at work.

What part they play in the COVID-19 pandemic: “This has an interesting backstory, because prior to COVID-19, ‘shelter-in-place’ was used for mass shootings. They were warning words used to alert people about a mass shooter and instruct them to find a safe place to stay in until everything was clear,” Hidalgo said. “It gained some traction during the coronavirus pandemic; but most leaders opted to use ‘stay-at-home’ instead, which was not associated with mass shootings. It was also more adaptable for requests being made of cities and states, for people to stay at home and only leave their home for essential reasons.”

For updates on the pandemic, click here to visit the federal government’s site. For more health news from the University of Alabama at Birmingham (UAB), click here.








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