Written by Ayuno
Edited by Sébastien
Figures by Airi, with Biorender.com
“Social distancing”, “wash your hands”, “flatten the curve”, “ça va bien aller”. Our lifestyle has changed dramatically since the beginning of the COVID-19 pandemic. But why? What is so special about COVID-19? Why do we have to be so scared of it?
COVID-19 stands for Corona Virus Disease 2019. So, COVID-19 is the disease itself, and the SARS-CoV-2 coronavirus is the virus that causes the disease. There are several different coronaviruses, some causing mild conditions such as the common cold, to some causing more serious diseases such as Severe Acute Respiratory Syndrome (SARS).
Viruses, including coronavirus, are not the same as bacteria. Bacteria are tiny living organisms. They can be found in many environments, such as soils, oceans, inside animals, and food products. Bacteria can eat (in a very broad sense) and reproduce. Some bacteria can be bad for us, causing food poisoning and Lyme disease. Other bacteria can be good for us, making things like yogurt and cheese, and even helping our digestion by living in our guts. In fact, we are covered with bacteria – some people think we have about the same number of bacteria (39 trillion) inside of us and on our skin as there are human cells in our body! Viruses are also tiny, but they are NOT living organisms. Unlike bacteria, viruses cannot survive without a living host, and they can only reproduce themselves by hacking their host’s cells. Because of this, many viruses reproduce in animals, and then “jump” to humans by chance. When this process causes disease, these diseases are called “zoonoses”. This is why you sometimes hear that the potential source of this new coronavirus is bats, a common animal for the spread of zoonoses because of their special immune system. Most of the time, viruses are not our friends, causing diseases in humans, such as rabies, influenza, or COVID-19.
Is COVID-19 really all that special? Like many viral diseases, COVID-19 spreads between humans through direct and indirect contact. Direct contact happens when you are close to an infected person, allowing the virus to get into your body. This can happen by kissing an infected person, hugging them, shaking their hand, or breathing in droplets the person sneezed/coughed/spat while talking. This is why people wear masks – to prevent them from spreading droplets in the air around them. These events let the virus to come into your body through your eyes, nose and mouth. This is why we are socially distancing. By not gathering with other people and avoiding crowding, we can reduce the risk of spreading the disease through direct contact. Indirect contact happens when you touch contaminated surfaces, and then touch your eyes, nose or mouth. Indirect contact does not require the physical presence of an infected person. This is why it is important to wash our hands with soap (or an alcohol-based hand sanitizer if none is available), avoid touching our faces, and disinfect surfaces. By using soap, viruses get washed off from our hands, hopefully before we bring them to our eyes, nose or mouth where they can enter the body. By disinfecting surfaces, we can reduce the risk of spreading the disease through indirect contact. In many ways, COVID-19 is like other viruses, which means infection can be prevented if we carefully follow safety measures.
If COVID-19 spreads just like other droplet-spread diseases, why are we experiencing a pandemic? At the moment, the answer is we do not know. Scientists are looking into what makes SARS-CoV-2 so infectious, with some finding that it is not actually that different from SARS-CoV-1, the virus behind the 2003 SARS epidemic, when it comes to the factors related to indirect contact. In other words, it does not appear that COVID-19 has become a pandemic because it can survive on surfaces longer than other coronaviruses. Similarly, it does not form aerosols, tiny droplets that can be carried by air currents, except under specific circumstances, like when putting a patient infected with COVID-19 on a ventilator, a machine that pushes air into their lungs to help them breathe. This means that maybe COVID-19 becoming a pandemic has more to do with direct contact. From the very beginning of the outbreak, it has been clear that people can have COVID-19 without any symptoms, and still spread the virus to others. There are many reasons why some people may not show symptoms of an infectious disease like COVID-19, but a common one is when a disease has an incubation period. The incubation period is the time between catching the disease and showing symptoms. For example, seasonal influenza (the flu) has an average incubation period of 2 days. So, after 2 days of being infected by the influenza virus, most people would start developing a fever and headaches, making aware that they may be sick and should not attend gatherings. The incubation period of COVID-19 is 5 to 6 days on average, but it can also be anywhere from 1 to 14 days. This means that you could be spreading the disease without knowing it for two whole weeks! Often, and especially with a deadly disease like COVID-19, doctors and public health officials do what’s known as “contact tracing” to figure out who may have been exposed to a sick person. Because COVID-19 can take several days to show symptoms while still being contagious, contact tracing can be very difficult – a lot can happen in two weeks. This is why social distancing, staying at home as much as possible, and wearing a face mask to protect others is important. By the way, the symptomatic duration of COVID-19 is also longer (6 to 9 days) than influenza (typically 3 days), adding more days to the duration you can be contagious.
So, is COVID-19 special? The answer is yes, because it has had such an impact on our way of living, beyond just knowing how to wash our hands properly! Through this lockdown, we are faced with our need for social interaction as a species. And, as abstract as it may have sounded before, we now understand the meaning of “flattening the curve”. We do not have a cure nor a vaccine against COVID-19 yet. But, while scientists around the world are working around the clock, we are supporting them and healthcare workers by slowing down the spread of the virus through measures like social distancing. There have been countless diseases in human history. Many of them were once believed to be an insurmountable challenges, but many of them are now curable or can be vaccinated against. Let’s hope that COVID-19 will join these solved diseases.
To learn more about COVID-19:
N van Doremalen, et al. Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1. The New England Journal of Medicine. DOI: 10.1056/NEJMc2004973 (2020). (https://www.nejm.org/doi/full/10.1056/nejmc2004973)
(Sender, Fuchs, & Milo, 2016)
Sender, R., Fuchs, S., & Milo, R. (2016). Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans. Cell, 164(3), 337-340. doi:10.1016/j.cell.2016.01.013
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