Coronavirus information changes quickly, so please take note of this story’s publication date. You can find current recommendations and national outbreak data on the CDC website. Or, if you want local coronavirus updates and stats, check out the department of health website for your state or your city. Enjoy reading and stay safe. Let’s flatten that curve.
The coronavirus has changed how we talk to one another — mostly through screens or 6 feet apart. It’s also influenced what we talk about. In the past two months, a number of concepts from epidemiology and infectious disease medicine have made their way into everyday conversation. While some coronavirus terms are self-explanatory, others aren’t.
“This thing is spreading like wildfire, and there’s a lot of confusion,” says Dr. Daniel Musher, an infectious disease specialist at the Veterans Affairs Medical Center in Houston and a professor at Baylor College of Medicine. With help from Musher, we compiled a list of essential terms to know in the time of the coronavirus.
With airborne transmission, disease particles can remain suspended in the air for a long time. So, if an infected person spends time in a room and then leaves it, someone else can enter that now-empty room and contract the virus. Airborne viruses, such as measles and smallpox, are highly contagious. Nine out of 10 people exposed to measles will get it if they’re not protected.
Initially, health officials said the coronavirus wasn’t airborne. The virus is thought to primarily spread when an infected person sneezes or coughs (or even just breathes), emitting respiratory droplets that make their way into someone else’s eyes, nose or mouth.
A study published March 15 in the New England Journal of Medicine found that the virus can stay suspended in tiny droplets, called aerosols, for up to a half hour. According to the New York Times, the study indicates that the “virus does not linger in the air at high enough levels to be a risk to most people who are not physically near an infected person. But the procedures health care workers use to care for infected patients are likely to generate aerosols.” The WHO is considering recommending “airborne precautions” for healthcare workers.
Musher says it’s really still uncertain whether or not the coronavirus is airborne. Exactly how a disease spreads is difficult to determine, he adds, and requires extensive research.
For now, most people seem to be contracting the coronavirus from close contact with an infected person. Experts define close contact as being within 6 feet of another person — that’s the recommended amount of space to keep between you and anyone who is or might be infected with the coronavirus. Countries with a high number of cases are being even more cautious. In Italy, for example, the government is asking everyone to stay one meter (a little more than 3 feet) away from one another in public spaces.
A growing number of people are contracting the coronavirus without knowing where or how they might have picked it up. This is called community spread (defined by the Centers for Disease Control and Prevention as “spread of an illness for which the source of infection is unknown”), and it’s a sign of an intensifying outbreak. In a recent case in Washington, DC, for example, one man who contracted the coronavirus had no known contact with anyone else who’d tested positive.
Containment (vs. mitigation)
In the public health world, containment happens during the early stages of an outbreak, when it’s still feasible to isolate infected people and thereby prevent the disease from spreading. Containment strategies include finding the source(s) of an outbreak, tracing their movements and implementing quarantines. As a disease escalates, the next step is mitigation: Governments operate under the assumption that new cases of the disease can pop up anywhere. To curb its spread, health officials take larger-scale measures, such as closing schools and canceling large events. As of Sunday, according to the US Surgeon General, the US response has shifted to mitigation.
Epidemic (vs. outbreak and pandemic)
The terms outbreak, epidemic and pandemic are often used interchangeably, but they each mean something different. An outbreak is a sudden, localized emergence of a disease. If an outbreak spreads to a wider area and infects many more people, it becomes an epidemic. A pandemic is the next level up — it describes a disease affecting an entire country or the whole world. The coronavirus is now classified as a pandemic by the World Health Organization.
Flattening the Curve
This phrase, commonly used by epidemiologists, has gone mainstream. The gist: We should do what we can now (e.g., going hard on social distancing) to slow down the spread of the virus because it’s better to have a drawn-out outbreak with a more even distribution of cases. If everyone gets the coronavirus within a short timeframe, it will overwhelm the healthcare system. A slow trickle of coronavirus patients won’t strain our resources as much (hospital beds, respirators, nurses, etc.), ultimately leading to fewer deaths.
Important to remember that #Covid-19 epidemic control measures may only delay cases, not prevent. However, this helps limit surge and gives hospitals time to prepare and manage. It's the difference between finding an ICU bed & ventilator or being treated in the parking lot tent. pic.twitter.com/VOyfBcLMus
— Drew A. Harris, DPM, MPH (@drewaharris) February 28, 2020
If someone contracts a virus (and gets sick from it), some amount of time will pass before they start showing signs of infection. That symptom-free, in-between stage is the incubation period. So far, health officials say, the incubation period for the coronavirus appears to range from two days to 14 days, lasting about five days on average. That’s why the CDC advises 14-day quarantines for Americans who’ve recently traveled to countries with a “Level 3 Travel Health Notice.” The most common symptoms during the incubation period are fever, a dry cough and trouble breathing.
The coronavirus is primarily being transmitted via respiratory droplets, which are microscopic drops of saliva or mucus (or other bodily secretions, potentially) that contain particles of the virus. When an infected person sneezes or coughs, these infectious droplets can find their way into the noses, mouths or eyes of people nearby. It’s thought that a cough can propel respiratory droplets about six feet through the air.
To assess the likelihood of a new infectious disease spreading, health officials use a metric called basic reproduction number, or R0 (pronounced R-naught). R0 is the average number of people who will contract a disease from a single infected person, within a population that has no immunity to the disease.
R0 of 1 is the cutoff point for whether a disease is likely to spread or die out. That means, if each person infected with a disease will give it to more than one other unprotected person, on average, spread is likely.
So far, most researchers who’ve put out R0 estimates for the coronavirus have placed it between 2 and 3. For reference, R0 for the seasonal flu is 1.3, while measles has an R0 of 12-18.
If you recently traveled to a country under a coronavirus travel advisory, or you were in the same place as someone who tested positive for the virus, you might be asked to keep close tabs on your health for a period of time. The CDC says to take your temperature twice a day to check for fever and stay alert for a cough or any breathing problems. This behavior is called self-monitoring. If you develop symptoms, isolate yourself, limit contact with others and call your doctor.
Self-quarantine (vs. self-isolation)
Governments have asked thousands of people who may have been exposed to the coronavirus to stay home. Self-quarantine is for healthy people who might be sick after being exposed to someone with the coronavirus. These potentially infectious people are supposed to stay inside for 14 days, avoiding contact with others and looking out for symptoms.
Self-isolation is for people who are a danger to others because they’ve actually tested positive for the coronavirus. People in self-isolation are being asked to stay home — no work, no school, no errands — and confine themselves to a room where they won’t have contact with other people or pets.
A “hot term,” according to Trump. Social distancing is an old disease-mitigation strategy, used to save lives during the Spanish flu of 1918. The CDC defines social distancing as “remaining out of congregate settings, avoiding mass gatherings, and maintaining distance (approximately 6 feet) from others when possible.” Congregate settings mean “crowded public places where close contact with others may occur.”
In the earlier stages of an outbreak, before community spread begins, the CDC only recommends social distancing for asymptomatic people if they have at least a medium level of disease exposure risk. (Here’s what that means.) If an outbreak progresses the point of “sustained community transmission,” risk exposure becomes harder to assess, and social-distancing measures may be advised across the board. For the coronavirus, nationwide social-distancing policies are now in place, for everyone.
The coronavirus is thought to be zoonotic, which means it spread from animals to people. Zoonotic diseases can be dangerous to humans because our immune systems haven’t learned how to attack them. Experts believe the virus originated in bats, although it’s unclear which animal was the intermediary that transmitted it to humans. The CDC estimates that 3 in 4 new human diseases now come from wildlife or livestock.