By now you’ve probably heard of COVID-19, or coronavirus disease discovered in 2019, which is responsible for a global pandemic. COVID-19 is caused by SARS CoV-2, or severe acute respiratory syndrome coronavirus 2, because it’s genetically similar to the SARS coronavirus which was responsible for the SARS outbreak in 2002. 

Now, coronaviruses that circulate among humans are typically benign, and they cause about a quarter of all common cold illnesses. In COVID-19 what happened is that there was a coronaviruses circulating among bats, which are a natural animal reservoir, that seems to have mutated just enough to start infecting an intermediate host - the pangolin, an animal that looks like a cross between an anteater and an armadillo. In late 2019 the coronavirus mutated again and started causing disease in humans. The outbreak began in China, but has since spread around the world. 

As of March 9, 2020, or roughly 3 months into the outbreak, there have been 109,578 confirmed cases of COVID-19 and 3809 deaths, resulting in a fatality rate of 3.5%. But that represents an average across different countries and timeframes. Based on a large study in China, digging deeper reveals that the fatality rate in China was actually 16% for cases between Jan 1 through Jan 10, then fell steadily over time, until it was only 0.8% for patients with symptom onset after February 1st. There are two main reasons for this. First, the hospitals and clinics were initially overwhelmed and couldn’t manage the disease, so both patients and healthcare providers were getting severely ill and dying. But within a few weeks, with better equipment, testing, and processes in place the healthcare system responded and brought down the fatality rate dramatically. Now as a point of comparison, the flu typically causes a fatality rate of 0.1%, so even based on this data COVID-19 is still 8 to 35 times more deadly than the flu. 

It’s also worth pointing out that for COVID-19 the mortality rates differ by group. So for example, if you split things out by age you can see from this table the fatality rate is relatively low if you’re below 60, with no deaths seen in children 9 and younger, but then 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 typically have a lot of these conditions so it’s not surprising that they go hand-in-hand.

Now, although the COVID-19 pandemic still ongoing, the good news is that in China and also in South Korea, the number of new cases per day has dropped off, largely due to the aggressive public health measures like  quarantining, aggressive testing, and ensuring hospitals have the right equipment and staffing.

Based on the current data, over 80% of the patients with COVID-19 have a mild infection, and some people don’t develop any symptoms at all. For others, they can develop symptoms that can range from mild symptoms like fever, cough, and shortness of breath, all the way to serious problems like pneumonia. Severe lung damage can cause acute respiratory distress syndrome, or ARDS, which 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 septic shock are the main cause of death for people with the infection, and again this is most likely to occur in those over the age of 60, smokers, and people with other medical conditions like heart disease. 

In addition to causing disease, coronaviruses can spread quickly. Usually the virus spreads when people cough or sneeze, and tiny droplets containing the virus are released. These droplets can land on another person’s mouth, nose, or eyes, and that allows the virus to enter a new person. When a person with COVID-19 travels to a non-affected area, this is called an imported case. If they start spreading the disease to household contacts and those around them, it’s called local transmission since it’s usually isolated to a small area and can be easily traced back to the original person. However when people begin to contract the disease without a clear source it’s called community transmission. To prevent or contain community transmission, some schools and businesses have shut down and some conferences, sporting events, and other large gatherings have been postponed or cancelled.  

Once a person is infected, symptoms develop about 5 days later. This is called the incubation period. Now there’s debate about how much asymptomatic people or presymptomatic - folks that are in the incubation period - are spreading the disease, and it may be much more than what was originally thought. Viruses are given a reproductive number or R-naught based on how quickly they spread, and person to person transmission has been confirmed both in and outside of China. An R-naught of 1 means that an infected person passes it on to 1 new person, an R-naught of 2 means that 1 person spreads it to 2 new people, and so forth. If the R naught is below 1, the infection peters out, if it’s 1 it stays steady, and if it’s above 1, then it continues to spread. The current estimate for COVID-19 is an R naught of 2.2. As a point of comparison, the R naught of the flu virus is about 1.3, so COVID-19 spreads quite a bit more easily.

To confirm the diagnosis, a reverse transcription polymerase chain reaction or rt-PCR test can be done, which can detect very small amounts of viral RNA. It’s worth mentioning, however, that early in the disease, the rt-PCR can often miss the infection altogether - meaning that it’s not very sensitive. So if severe pulmonary disease is suspected, a chest CT should also be done to help detect the presence of a viral pneumonia. It’s also important to look for other causes of similar symptoms; by doing things for example, like a quick flu test or a respiratory viral panel to look for alternative causes of the symptoms.    

Treatment is focused on supportive care such as providing fluids, oxygen, and ventilatory support for really ill people. There’s also early data showing that Remdesivir, an antiviral drug previously used against Ebola, can be helpful, and it’s being tested in large scale clinical trials in the US and China.

Unfortunately there’s no vaccine currently available to protect against COVID-19. Having said that, there are some being researched including one that is in clinical trials and will likely be ready in 2021. So the main goal is to avoid person to person transmission. In areas with community transmission, anyone with mild symptoms - regardless of whether they have been diagnosed as having COVID-19 or not, should wear a mask and they should self-quarantine within their home. If those symptoms worsen, they should call their clinic or use telemedicine to talk to a clinician. For people with symptoms that live with others or even with pets, they should self-quarantine in a seperate room and use a seperate bathroom if possible, and they should avoid sharing household items like bedding or eating utensils. In fact, there has been a confirmed case of human-to-dog transmission, where COVID-19 went from a person to their dog. The dog didn’t get sick and there’s no evidence that pets can spread this disease or become sick, so it's not necessary to take measures against companion animals. Finally, anyone with symptoms - including children and younger adults - should not attend school, work, or any other in-person gathering, and should avoid travel. 

Now, for individuals that don’t have symptoms but are at higher risk like those over age 60, and people with a chronic disease, the recommendation is that they also self-quarantine to avoid the chance of getting sick. Self-quarantining requires keeping a few weeks supply of your medications, groceries, and household items within reason, as well as having an emergency contact person. 

Coronaviruses don’t usually spread over long distances in the air, but they can get flung from one person to another on tiny droplets of saliva, when someone’s coughing or sneezing. In addition, some strains of coronavirus can survive on surfaces for over a day. With that in mind, if you’re a healthy person living in a non-outbreak area, the recommendation is to avoid travel to disease outbreak areas, generally stay away from crowded places, and stay at least 6 feet or 2 meters away from anyone with symptoms. Wearing a surgical mask is not recommended because they’re meant to catch droplets from a cough or sneeze from going out, rather than preventing you from breathing in the virus. Similarly wearing an N95 mask is not recommended because they're only meant to be worn by healthcare workers. In addition, cleaning and sterilizing frequently touched surfaces like toilet seats, door handles, phones, and keyboard, is also a good idea. As always, careful hand washing is key and it should be done with soap or alcohol-based hand sanitizers and scrubbing for 20 seconds. Also, avoid touching your eyes, nose, and mouth—this is the area, known as your T-zone, is a common entry point for viruses into the body.

For healthcare workers who are around people with COVID-19, the recommendation is to apply droplet and contact precautions. That includes wearing personal protective equipment like a clean, dry surgical mask, gloves, long-sleeved gowns, and eye protection like goggles or a face shield. When performing a procedure that generates aerosol, like tracheal intubation, bronchoscopy, CPR, or noninvasive ventilation, it’s important to wear a N95 respirator. This prevents 95% of the small particles, like respiratory droplets, from passing through. 

To recap, the SARS-CoV-2 virus causes COVID-19. The virus travels in respiratory droplets and enters the body via the mouth, nose, or eyes. It can cause symptoms like fever, cough, and shortness of breath, and in some people can progress to more dangerous complications like pneumonia, ARDS, and septic shock. The highest risk is among the elderly and those with other serious health conditions. Treatments are focused on supportive care, but medications like Remdesivir are in clinical trials and there’s a vaccine in clinical trials that will likely be ready in 2021. In the meantime, the best strategy is prevention -- this includes careful hand washing, avoiding travelling to disease outbreak areas and crowded places when possible, avoiding touching your T-zone, and if you’re a healthcare worker to use personal protective equipment.