Coronavirus disease 19 (COVID-19)

Definitions & Key takeaways

COVID-19 is a novel coronavirus that was first identified in 2019. COVID-19 is caused by a virus called SARS-CoV-2. So far, it's proved that COVID-19 is transmitted through respiratory droplets, which can enter another person's body through the respiratory tract, the mouth, or the eyes. The incubation period is generally around 4 or 5 days but can take up to 14 days. Common symptoms include fever, cough, shortness of breath, and fatigue. People can also present with loss of smell and taste and pulmonary fibrosis.

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Coronavirus disease 19, or COVID-19 for short, is caused by a pathogen called SARS CoV-2, or severe acute respiratory syndrome coronavirus 2.
So from its name alone, “severe acute respiratory syndrome coronavirus,” you get that this pathogen is a type of virus that causes a respiratory infection.
The number two is in the name because this virus is genetically very similar to the SARS coronavirus, which was responsible for the SARS outbreak of 2002.For someone to become infected with COVID-19, all 6 steps in the chain of infection model must be met.
In order, these include: the pathogen, the reservoir, the portal of exit, the method of transmission, the portal of entry, and, finally, the susceptible host.
So for COVID-19, the pathogen is COVID-19, and the reservoir is a place where the virus can survive. Right now, the natural reservoir for COVID-19 is still being investigated.
Both symptomatic and asymptomatic humans who are infected with COVID-19 can act as reservoirs. The virus is then released from the reservoir through a portal of exit, like the respiratory tract.
Transmission can happen through respiratory droplets. When people cough or sneeze, they can spread the virus directly to other people, or those droplets could end up on surfaces like phones, tables, doorknobs, and faucets.
The droplets then enter the respiratory tract as well as the mouth or eyes as the portal of entry. Finally, the virus then infects a susceptible host, which is, well, another person.
Once a person is infected with COVID-19, there’s an incubation period, which is the time between infection and symptom development.
For COVID-19, the incubation period can last for up to 14 days but is usually around 4 or 5 days. Some people don’t develop symptoms at all, but they can still transmit the virus to other people.
Others develop symptoms, which can range from mild to severe. Mild symptoms include fever, cough, shortness of breath, fatigue, and loss of smell and taste.
Serious problems include pneumonia, and if there’s severe lung damage, that can cause acute respiratory distress syndrome, or ARDS.
This occurs when the lung inflammation is so severe that fluid builds up around and within the lungs. The severe infection can cause septic shock, which happens when the blood pressure falls dramatically, and the body’s organs are starved for oxygen.
ARDS and shock are the main cause of death for people with the infection. Finally, it’s worth noting that even folks that don’t die from COVID-19, including young and healthy individuals, can go on to develop pulmonary fibrosis, which is a chronic lung condition that can severely impair a person’s quality of life.
Finally, in terms of fatality, the data shows that COVID-19 fatality rates differ by group. So, for example, the fatality rate is relatively low if you’re below 60 with no deaths seen in children 9 and younger.
However, the rate starts to really climb up for the elderly, so they’re really the ones at highest risk. Similarly, the fatality rate is higher for folks with hypertension, diabetes, cardiovascular disease, chronic respiratory disease, and cancer relative to folks without any of these conditions.
And of course, the elderly are more likely to have a lot of these conditions, so it’s not surprising that they go hand-in-hand.
All right, as a quick recap...COVID-19 is caused by a virus called SARS CoV-2. For someone to become infected with SARS CoV-2, the 6 steps in the chain of infection must be met.
These are the pathogen, the reservoir, the portal of exit, the method of transmission, the portal of entry, and, finally, the susceptible host.
The incubation period can last for up to 14 days but is usually around 4 or 5 days. When symptoms develop, they can range from mild, like fever, cough, fatigue, shortness of breath and loss of smell and taste, to severe like those seen with pneumonia.
Common short-term complications of COVID-19 are acute respiratory distress syndrome and septic shock, while pulmonary fibrosis is a known long-term complication.