COVID-19 or coronavirus disease discovered in 2019, is responsible for a global pandemic. COVID-19 is caused by a virus called 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. 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 were coronaviruses initially circulating among bats, which are a natural animal reservoir, that seems to have mutated and ultimately started causing disease in humans. The outbreak began in China, but has since spread around the world. Worldwide, as of August 1st, 2020, or roughly eight months into the outbreak, there have been about 18 million confirmed cases of COVID-19 and 681,000 deaths, resulting in a fatality rate of approximately 4 percent. However, current studies suggest that the actual fatality rate is likely to be lower, around 0.7 percent. The reason for this is that there are a lot of undiagnosed COVID-19 cases, which makes the actual number of cases go up. Many of these are asymptomatic carriers. In fact, the National Institute of Allergy and Infectious Diseases has estimated that 25-50 percent of the cases may remain asymptomatic. During this worldwide pandemic, there are many lessons to be learned from how different countries have responded to the disease. To explore that, let's use an epidemic curve which shows the number of new cases in a country seen each day. The horizontal line represents the capacity of the healthcare system within that country. Healthcare capacity accounts for things like the number of beds and ventilators, as well as the number of health care workers and resources like personal protective equipment or PPE they have available. Usually, the healthcare system is working near full capacity, so when a pandemic like COVID-19 breaks out, even a relatively small increase in the number of patients can overwhelm the healthcare system. The two strategies to tackle this problem are to flatten the curve and raise the line. Flattening the curve is focused on diminishing the total number of people that get sick and slows down the rate at which new people get sick, while raising the line helps to actually increase healthcare capacity. Let's take a look at how different countries apply these two strategies, starting with China, the first country to deal with COVID-19. China informed the World Health Organization about COVID-19 on December 31st, 2019. A few weeks later, on January 24th, China aggressively tried to flatten the curve by placing a major lockdown on the Hubei province and then issued similar lockdown on other regions within China. Authorities forced residents to stay at home except for essential activities like going to the pharmacy or getting groceries. Non-essential businesses and schools were shut down, public transportation was shut down and roads between cities were blocked off. Going even further, some communities enforced a system by which there was only one entrance and exit and everyone passing through was screened for symptoms of COVID-19. If anyone in the community tested positive, the entire community might be quarantined. In all, this affected 15 cities and about 57 million people. The measures were swiftly enacted and strictly enforced, and 12 days later on February 5th, the exponential growth broke and the number of new cases started to fall off. Meanwhile, given how many cases there already were at that point, China made efforts to raise the line. They built multiple hospitals dedicated to COVID-19 patients and flew in doctors and nurses from less affected regions of the country to staff these hospitals and kept them protected with well designed PPE that covered them from head to toe. By March, the economy began to return to normal and China was seeing more cases of COVID-19 from travelers than from their citizens. Now, let's look at South Korea, which took a slightly different, yet equally effective strategy. To flatten the curve, they implemented mass testing that was free, easy, and accessible. They offered drive-through testing stations, where people were tested inside their car. They also had phone booth-like testing areas where the person walks in, gets tested and walks out. South Korea was performing 15,000 tests per day. By July 29th, they had tested around 1,547,307 people out of a population of 51 million, which works out to one out of every 33 people. Those who tested positive were either sent to a hospital if their symptoms were severe, or to a quarantine facility if the symptoms were more mild. At the same time, public health workers conducted contact tracing for every case, to track down individuals that might have been exposed to the virus. Because South Korea had such a thorough understanding of who did and didn't have COVID-19 and where they had been, the lockdown was effectively done at the level of the sick individual rather than at the societal level like in China. Given the fore warning that South Korea had about the disease and the aggressive efforts around case identification, their healthcare system was well prepared for the patients, and had the resources to keep healthcare workers safe. Next, let's look at the United States, which has the most cases in the entire world, and where the number of cases continues to rise quickly. In terms of testing based on August second data, the US has about 52,942,145 people tested out of a population of over 332 million, which works out to one out of every six people. Even though this testing rate is quite high, most often the results take days to come in or are unavailable altogether. This means that by the time the test results are ready, the infected person has already gone about spreading the virus to others. In addition to the absence of widespread testing to identify which individuals need to be isolated, only some United States have mandated a lockdown, and even when it's applied, there has been minimal enforcement. In some, without a federal mandate or enforcement of a lockdown, it's been largely a scattered state-by-state effort that has mostly been voluntary. In terms of raising the line, healthcare workers have generally had inadequate PPE, especially N95, to feel safe. As a result, hundreds of physicians and nurses have gotten ill or been quarantined. Meanwhile, intensive care units or ICU beds have started to run out. Ventilators are in short supply and there have been runs on medication like hydroxychloroquine. Unfortunately, in the context of having scarce healthcare resources, we know that mortality rates can be quite high. Now, here's the good news. A complete lockdown, meaning one that's enforced rather than voluntary, so that the maximum number of people abide by it can stop the spread of COVID-19 within a matter of days even in a country that is seeing exponential growth like the US. To show how this works, let's start with a community that's already seen an exponential growth in COVID-19 cases. Most folks with COVID-19 have mild symptoms or have just gotten it and haven't begun showing symptoms yet. There are two options at this point. Option 1, is to let things continue with a voluntary social distancing policy where some adhere to it while others continue to throw pool parties, keep businesses open, and invite relatives over for dinner. In that scenario, even with the best of intentions and cleaning precautions over the next two weeks, there's still going to be an exponential growth in cases causing hospitals to fill up with patients and many people will die. But, now consider option 2. Option 2, there's an enforced lockdown with absolutely everyone confined to their home. If that were to happen, the virus could spread to household contacts but after that, the transmission would abruptly end. As these infected people recover with no access to new hosts, the virus basically has no place to go and within two weeks, the number of new cases starts to fall. Fewer cases means that the healthcare system doesn't get overwhelmed and the mortality rates fall because everyone who needs care can get it. This approach and timeline is based on real data from Hubei where they implemented option 2. The rate of new cases decreased within a few days of lockdown, and because there's a lag between people getting sick and going to the doctor. That decrease was seen about two weeks later in terms of fewer new cases coming to the hospital. The bottom line is, voluntary social distancing is only as effective as the number of people who are practicing it. If enough people don't adhere, then the virus can continue to spread and the pandemic drags out, ultimately resulting in more deaths. Now as of August 1st, for a variety of reasons, especially economic ones, many countries around the world as well as many US states, had to ease some of the restrictions enforced. However, when social distancing measures are relaxed too quickly, there's a higher risk of experiencing a second even larger wave of infected individuals. This is exactly what we encountered in 1918 with the influenza pandemic, commonly known as the Spanish flu pandemic. That pandemic was caused by a strain of the H1N1 influenza virus and infected about 500 million people worldwide and killed 50 million people. Now, the Spanish flu pandemic occurred in three waves. The first wave was in March of 1918, the second wave was in the autumn of 1918, and the third wave was that winter and in the spring of 1919. In fact, the second wave was more deadly than the initial one, presumably due to the fact that it was spreading on crowded trains and in field hospitals and camps during World War I. In fact, even though the third wave was less deadly than the second one, it was still more severe than the original. Now, it's also important to remember that in 1918, health care workers were limited and viral diagnostic tests, vaccines, antiviral drugs, and antibiotics were basically nonexistent. Although some cities enforced measures such as shutting down schools and prohibiting public gatherings, it wasn't a widespread national effort. Bottom line, for COVID-19 we have more tools available, but the lessons are clear for what happens when we start to congregate in groups. The chance for outbreaks and an overall surge goes back up and if the virus does spike again in the fall or winter during or near the peak of the seasonal flu season, the consequences could be even more devastating. Looking at the current pandemic over the last month, some countries like Australia and Japan started lifting restrictions and have already seen a surge in the number of cases. The surge can largely be attributed to some people disregarding social distancing norms and gathering in pubs and restaurants. On the other hand, countries like New Zealand that managed to contain the first wave have not seen case surges after relaxing the restrictions. Now in terms of mortality, the data shows that COVID-19 mortality rates differ by group. 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 few deaths seen in children nine and younger. Then it starts to really climb up for the elderly. They are 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. Of course, the elderly typically have a lot of these conditions. It's not surprising that they go hand in hand. Now, although children are less likely to develop a serious disease, they can definitely spread the virus and actually they can be even more contagious than adults since they usually practice worse hygiene habits. One other group is pregnant people, and the data has been sparse, but it seems like healthy pregnant people are not at high risk for developing serious disease and to date, there haven't been reported cases of intrauterine transmission of COVID-19. The virus also wasn't detected in the breast milk of a small group of mothers with COVID-19. In terms of breastfeeding, the main risk would still be from droplets rather than through the milk itself. However, early data from a UK study suggests that pregnant women with COVID-19 might be at a slightly higher risk of developing severe illness during their third trimester. The study also found that pregnant women of black, Asian, or other minority ethnic groups might be at a higher risk of being hospitalized. All in all, this means that pregnant women should be more mindful about preventative measures. Now, overall, based on the current data, over 80 percent 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 mild symptoms like fever, cough, and shortness of breath. Other symptoms include fatigue and things like loss of smell and taste. Serious problems include pneumonia. If there's severe lung damage that 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 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, a chronic lung condition that can severely impair a person's quality of life. In addition to causing disease, coronaviruses can spread quickly. It's increasingly clear that a lot of spread is occurring through pre-symptomatic people, folks that are in the incubation period, many of whom are not at high risk themselves. It also spreads from those weak symptoms, like when people cough, sneeze, or even speak, and tiny droplets containing the virus are released. These droplets can land on another person's mouth, nose, or eyes, known as the t-zone, and that allows the virus to enter a new 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. Recent studies suggest that SARS-CoV-2 airborne droplets can remain infectious for up to three hours. In addition, the SARS-CoV-2 virus can also survive on surfaces. It can survive up to eight hours on latex and aluminum, up to 24 hours on cardboard, up to three days on counter-tops, plastic, and stainless steel, and up to five days on wood and glass. You can get infected by touching these surfaces and then touching your t-zone. That's why you should wash your hands with soap and water frequently, or clean them with an alcohol based hand-rub. Also make sure you clean and sterilize frequently touched surfaces, like phones, keyboards, door handles, and toilet seats with alcohol based cleaning wipes. Once a person is infected, symptoms develop about five days later. This is called the incubation period. Now, there's debate about how much asymptomatic people or pre-symptomatic people, those who are in the incubation period, are spreading the disease. It may be much more than what was originally thought. Now, this is where masks and facial coverings come into play. A study was done at a salon, where to stylists tested positive for Covid-19. However, contact tracing of a 139 of their clients revealed that all were asymptomatic. In addition, all those who volunteered to be tested for Covid-19 turned out negative. The reason for the virus not spreading is that both the stylists and the clients wore masks during their interaction. What happens when you wear a mask? Firstly, masks covered your t-zone, preventing the virus from directly landing on it. Secondly, it stops you from touching your t-zone with your hands, which may be contaminated if you've touched an infected surface. Most important of all, masks prevent an infected person from releasing saliva droplets into the environment. Now, following the issuing of mandates for face mask use in public, a study carried out in some US states found that the daily case rates had been reduced by about two percentage points in only three weeks. In addition, socially distancing alone is not enough, as small droplets have been shown to travel up to a distance of seven meters, or 23 feet. This is why masks are also a necessary part of prevention. Viruses are given a reproductive number, or are not, based on how quickly they spread. Person to person transmission has been confirmed both in and outside of China. An R-naught of one means that an infected person passes it onto one new person. An R-naught of two means that one person spreads it to two new people, and so forth. If the R-naught is below one, the infection pit is out. If it's one, it stays steady. If it's above one, then it continues to spread. The current estimate for Covid-19 is an R-naught of two to 2.5. As a point of comparison, the R-naught of the flu virus is about 1.3. 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. If severe pulmonary disease is suspected, a chest CT can be done to help detect the presence of a viral pneumonia. Next, newer rapid testing methods for Covid-19 can get the results within minutes. One of these is isothermal amplification, which also checks for viral RNA. The other is rapid serological testing, which checks for antibodies created by the immune system to fight the virus. Since it's checking for antibodies made by the body, it can detect previous infections even after the virus is gone. Finally, 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. In terms of treatment, individuals with mild symptoms should isolate themselves at home so they can improve with rest and fluids. For those with severe symptoms, treatment is focused on supportive care such as providing fluids, oxygen, and ventilatory support for really ill people. Also, recent studies have found that those requiring supplemental oxygen or ventilator support may benefit from being placed in a prone position or lying face down on the bed. Prone positioning has been found to improve ventilation in the back parts of the lungs, which improves the oxygen saturation and might even reduce the need for intubation. There's early data showing that remdesevir, an antiviral drug previously used against ebola, can help shorten the duration of symptoms though without significantly improving recovery time. A multinational randomized control trial done on 1,063 individuals hospitalized with COVID-19 showed a shorter clinical recovery time with remdesevir compared to placebo. Other medications that were initially thought to be beneficial against COVID-19 include lopinavir and ritonavir, both of which are antiretroviral drugs, and chloroquine and hydroxychloroquine, which are usually used to treat malaria. However, recent studies show no clinical benefit in using these medications in treating COVID-19. Two treatment options have shown promising results in preliminary trials. These include dexamethasone, which is a corticosteroid and convalescent plasma therapy or CPT. A study done in the UK showed that dexamethasone reduced mortality in critically ill individuals with COVID-19. On the other hand, convalescent plasma therapy is based on the principle of transfusing infected individuals with the plasma of someone who has already recovered from COVID-19. The anti-COVID-19 antibodies in the plasma provide passive immunity to fight the infection. Although the efficacy of CPT in treating COVID-19 is still not clear, there has been increasing evidence to suggest that it's safe. To back this up, a recent study done by the Mayo Clinic showed that CPT causes severe adverse reactions in less than 1 percent of transfusions. Vaccines are also being developed in countries around the world and it's estimated that they'll be available in 2021. To recap, eight months after the start of the COVID-19 pandemic, countries around the world have had varying levels of success in containing the disease. This is done by flattening the curve and raising the line. Some countries like China and South Korea have decreased the number of cases, while in the US, the number continues to rise. A mandated lockdown at a federal level to enforce social distancing, mass testing, and contact tracing are key components to preventing the spread of the disease, while raising the line can be accomplished by training more frontline healthcare workers, building more hospitals and providing hospital staff with adequate PPE. Treatments are focused on supportive care and a number of medications are in clinical trials. There may be a vaccine ready in 2021. For individuals the best strategy is prevention, this includes: staying isolated, careful hand washing, avoiding touching your T-zone, and wearing a mask when outdoors or in a crowd. If you're a healthcare worker, you should use personal protective equipment.