By: Ahmad M. Rashid, MD, pulmonary and critical care physician, National Jewish Health
October 21, 2020
Question: What do these very different locations have in common?
Answer: They all became centers of COVID-19 spread and hot spots for super-spreader events because of the three Cs of coronavirus — Contact, Closed, Crowded. As winter approaches, there is real concern about a resurgence in COVID-19 numbers. It’s important to remind ourselves of how the virus spreads, what can we do to minimize our risk. Let us look at some of the factors that make it easier for the infection to spread.
In the last eight months, multiple studies have shown that coronavirus transmission happens easily when you have:
CONTACT with infected person(s), in CLOSED (poorly ventilated) and CROWDED spaces.
SARS CoV2 is a respiratory virus that causes the COVID-19 disease. It spreads through person-to-person CONTACT, mainly through droplets laden with virus that comes out of an infected person’s mouth and nose. Under certain circumstances, smaller particles called aerosols may spread the disease as well, but it is rare in day-to-day life. You can also get infected by touching (CONTACT) a surface soiled with fresh, infected droplets and then touching your mouth, nose or eyes.
COVID-19, like other respiratory infectious diseases, is frequently transmitted when you are within six feet of a person who has COVID-19, especially early on in their infection. This is called close CONTACT.
Public health professionals can predict infection spread when they have information about the close social contacts of people diagnosed with the disease. The most common way to measure social contacts is to ask people to report, for a certain day, how many contacts they made with people in different age groups and different social settings, and how long the contact time lasted. We call this contact tracing.
When we take a deeper look into contact tracing of people with COVID-19, we see patterns that show:
You have a higher risk of getting infected if you live with an infected person(s) which exposes you to CONTACT, CLOSED environments and possibly CROWDED spaces.
You have a higher risk of catching the infection if you share a workspace close to someone who is infected (see photo at right for example of CROWDED, CLOSED workspace with high risk of CONTACT).
Living in a multi-generational family home gives you a higher chance of getting the coronavirus infection, especially for older family members (due to close CONTACT in CROWDED and CLOSED spaces).
Photo Credit: People Before Profit
The higher the viral load that an infected person has, the more likely they are to spread the infection to others. Studies have shown that an infected person is most likely to infect others two days before having symptoms until about five days after symptoms began.
COVID-19 symptoms can include the typical fever, cough and nasal congestion, and also the unusual symptoms of new loss of taste and smell, abdominal pain and diarrhea.
Some people don’t have symptoms at all (asymptomatic) and still transmit the disease. And some people, for reasons unknown, spread the infection more efficiently compared to how others spread the disease. We also know that younger people who have no or mild symptoms can also spread the virus.
So far, most studies support the fact that the SARS-CoV-2 virus (that causes the COVID-19 disease) spreads more efficiently in CLOSED, poorly ventilated and CROWDED environments. This risk increases if people are talking loudly, singing or breathing heavily in crowded, poorly ventilated spaces such as indoor group singing or exercise. These type of outbreaks have been reported in youth camps, homeless shelters and churches.
Global data shows that certain social economic and racial groups are more susceptible to getting infected with COVID-19. In the U.S., the African-American and Hispanic populations have borne the brunt of the disease. People in lower social economic groups are more likely to be essential workers, more likely to use public transportation and more likely to have no or poor access to routine health care. All of those factors make it easier to get infected with coronavirus. Once infected, it may be difficult to safely quarantine if they have a multigenerational household without space to quarantine or if they are homeless. Lower social economic groups are also more likely to work in high-risk jobs such as meat packing plants.
We learned during the SARS outbreak in 2002-2004, that large outbreak clusters and super-spreading events increase overall infection rates in the community. At that time, epidemiologists defined a super-spreader as an individual who infects eight other people. A super-spreading event can happen when highly infectious people have CONTACT with others in large, CROWDED and CLOSED (poorly ventilated) spaces. This causes a lot of people to get infected and, once they get out in the community, they can spread it to their families and other contacts much more easily.
During the COVID-19 pandemic, super-spreading events have been recorded in China, Italy and the United States. One of the first clusters to appear was from a choir practice in Washington state.
Most of the time, it is impossible to tell whether a person is an asymptomatic carrier or a potential super-spreader. The best way to protect yourself and your family this fall and winter is to avoid large, crowded indoor spaces that aren’t adequately ventilated.
As the weather gets cooler and the days shorter, we will have fewer chances to get outside. Remember to avoid the three C’s this winter — CONTACT, CLOSED and CROWDED, and to practice the fourth and most important C word — “CARING.” Showing empathy, respect and caring for other people will help us get through this together. Stay positive!
Learn more about COVID-19 and how it affects specific health conditions in these printable patient education materials.
Download COVID-19 Materials