Beginning in December 2019, a small cluster of cases of a pneumonia of unknown origin was reported in Wuhan, Hubei Province, China. Genetic sequencing of samples taken from the respiratory tract secretions of those exhibiting the suspicious pneumonia revealed the causative agent as a previously unknown coronavirus initially named the 2019-nCoV virus (the "n" indicating a novel coronavirus). The virus was subsequently named SARS-CoV-2 (also styled SARS-CoV2). The disease caused by the virus is designated COVID-19.
Case counts grew rapidly in China and by January 2020 the virus spread to other countries. On March 11th, the World Health Organization (WHO) officially declared COVID-19 a global pandemic.
While SARS-CoV-2 is a coronavirus and not a seasonal influenza virus, many of the symptoms, treatments, and outcomes of their related diseases (COVID-19 and seasonal flu) are similar. COVID-19 is however, substantially easier to transmit and has a substantially higher fatality rate than seasonal flu. During the earliest stages of the pandemic, in some areas of the world the lethality rate recorded was hundreds of times that of normal seasonal flu.
As of early September 2020, scientists were still unsure of the exact origin of SARS-CoV-2 and of the full range of clinical conditions associated with COVID-19. Scientists continued to grapple with conflicting data about transmissibility in different age groups, dramatic difference in disease outcomes (especially lower death rates in children and younger adults), and the extent to which COVID-19 was spread by people who were asymptomatic (showing no signs of the disease).
In addition to dealing with potentially severe respiratory reactions leading to death, clinicians and medical scientists were gathering data and conducting research into observed associated vascular conditions, including myocarditis, and well as potentially increased vulnerabilities to diseases like diabetes. While the elderly and those with preexisting disease remained the most vulnerable in terms of severe illness and death, case counts among younger people soared globally and in the United States. With those increased case counts, hospitalizations of younger people suffering severe forms of the illness also rose. While death was rare in very young children, physicians still expressed concern over the potential for associated diseases like PMIS Pediatric Multisystem Inflammatory Syndrome (PMIS) as well as the longer term implications of the disease in children and younger adults.
While there was no definitive cure, clinicians were, however, beginning to better understand the course of the disease, including the wide variability in symptoms presented. A limited, but increasing, range of treatment options were available that showed some effectiveness in shortening the course of the disease and reducing the risk of death in some cases.
By 4 September, 2020, the Coronavirus Resource Center at the Johns Hopkins University of Medicine attributed 872,390 deaths globally to COVID-19, with 187,696 of those deaths occurring in the United States. The World Heath Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) cited approximately 26.5 million confirmed cases globally, with approximately 6.2 million of those cases confirmed in the United States.
The United States far surpassed the early record numbers of cases and deaths in China, Italy, and Spain. By September, Brazil was second hardest hit in terms of fatalities with 124,614 dead due to COVID-19. India attributed 68,472 deaths to COVID-19, Mexico 66,319 deaths, and the United Kingdom reported 41,616 dead.
In terms of case-fatality ratio, as of September 4, 2020, the ten hardest hit countries were Yemen (28.9 percent). Italy (13.0 percent) United Kingdom (12.1 percent), Belgium (11.4 percent), Mexico (10.8 percent), France (9.1 percent), Hungary (9.0 percent). Netherlands (8.3 percent), Chad (7.6 percent), and Sweden and Canada tied for tenth highest (at 6.9 percent). Although public health experts were openly skeptical of China's reporting methodology, China reported a 5.3 percent case fatality rate. While having the largest number of deaths, the United States had a 3.0 percent case-fatality ratio.
In terms of deaths per 100,000 population: Omitting limited data from the small countries of San Marino and Andora, the ten hardest hit major counties were Peru (90.9), Belgium (86.7), United Kingdom (62.6), Spain (62.6), Chile 61.0), Brazil (59.5) Italy (58.8), Sweden (57.3), the United States (57.1) and Mexico (52.6). Canada suffered 24.9 deaths per 100,000 people.
Even though most cases are mild, epidemiologists predicted that the overall penetrance of COVID-19 and soaring case counts could lead to more than a million deaths globally before the pandemic burns out.
Background and Scientific Foundations
Epidemiologists initially traced the outbreak to a wholesale food market in Wuhan sometime in early December 2019. The estimated Ro numbers observed were generally consistent with a single point source outbreak. However, high early case counts and a lack of direct links to the market by some early patients (14 of the first 41 documented clinical cases in China had no relationship or exposure to the market) raised the possibility that the viral leap from animals to human hosts took place earlier, and at another location within China. Such a scenario would be more consistent with the early COVID-19 generation times observed and subsequent super-spreading behavior, because people may have unknowingly passed the virus to others well before their first symptoms appeared. Several studies also indicate that the virus may have been spreading in humans earlier than December 2019.
The SARS-CoV-2 virus is genetically part of the same clade (taxonomic classification) of coronavirus as the Middle East respiratory syndrome coronavirus (MERS-CoV) identified after outbreaks in the Middle East in 2012, and the severe acute respiratory syndrome coronavirus (SARS-CoV, or SARS). Which was responsible for outbreaks of disease emanating from Guangdong Province, China, in 2003 and was spread globally, outside of China, by travelers.
Although the genetic relationships between coronaviruses can vary greatly in terms of percentage of shared genes, researchers in China claim that preliminary analysis shows that SARS-CoV-2 shares almost 80 percent of the genetic sequences found in SARS-CoV, and that SARS-CoV-2 is almost 96 percent identical at the genetic level to a known bat coronavirus. Researchers also cite evidence that SARS-CoV-2 enters cells in the same way, via the same cell entry receptor, as SARS-CoV.
Although fruit bats are considered one natural reservoir for SARS-CoV-2, there remains uncertainty as to the ultimate reservoir for SARS-CoV-2, and any intermediate animals that may have been in the transmission chain to humans.
Morbidity, mortality, and transmission
During the first months of the SARS-CoV-2 outbreak, the case fatality rate generally ranged between 1.8 and 4.6 percent, globally. In terms of disease impacts, this made the virus much more like the 1918 flu pandemic, rather than SARS or MERS. Lethality rates would normally be expected to be higher in areas without an adequate medical infrastructure. Moreover, the higher lethality rates observed are most likely an overestimate of the actual lethality because many cases are not confirmed, and in some areas go unreported by individuals who are either asymptomatic or have a mild case.
The equation for lethality rates (actually a lethality percentage) is: Lethality = (Number of deaths / Number of cases ) x 100. Lethality rates are expressed as 1 death per 10 cases, or one death in 20 cases, etc. For example: If a hospital in a town records 10 deaths from a disease where 100 cases were confirmed by laboratory testing, that would yield a lethality rate of 1 in ten cases or 10 percent. Yet if, hypothetically, only half of all cases are reported, then the estimated actual case count is 200 cases. With this increase in the denominator, the lethality rate becomes 1 in 20 cases or 5 percent.
In the modern world, and especially in countries with well developed health care and public health systems, deaths are difficult to hide. The number of deaths missed or misattributed to a disease is actually very small and so epidemiologists have a much high confidence in the numerator of the lethality equation (Number of deaths) than in the denominator (actual number of cases). The incidence (number of cases) is, in many cases, much larger with a disease like COVID-19; where a significant number of people contracted the disease may be asymptomatic or have such a mild illness that they weather it at home. In either situation, a case is fare less likely to be recorded than a death.
Studies indicated that SARS-CoV-2 could be transmissible before symptoms appeared and this greatly complicated quarantine efforts. Early studies showed that while 25 to 50 percent of infected people were asymptomatic, and another portion experienced only mild symptoms, both groups could be highly infectious. Even children who were asymptomatic showed high viral loads (high number of viral particles in their nose and mouth secretions) that could be infectious. This was not the case with SARS; only patients with symptoms were infectious. Control of infectious disease outbreaks normally rely on identification and isolation of infected individuals before they can infect others. Moreover, when a disease is transmissible before symptoms, those infected may not be detected by standard screening measures at small clinics, airports, and other checkpoints. Accordingly, epidemiologists argued that preventative social distancing across entire populations was necessary to break the chain of SARS-CoV-2 transmission.
Most cases of COVID-19 are mild, and many infected people develop no symptoms at all. Those who develop symptoms usually experience some or all of the following: fatigue, fever, chills, dry cough, muscle aches, sore throat, loss of the sense of smell or taste, diarrhea, nausea, vomiting, or congestion and runny nose. About one in six people with COVID-19 will develop more severe symptoms including difficulty breathing or severe fatigue. Pneumonia and respiratory failure are the complications responsible for most COVID-19 deaths, but the disease has also resulted in inflammatory conditions, stroke, heart attack, vascular insufficiency, postonset galucoma and neurological impairments.
Early in the outbreak, Covid-19 was most lethal for the elderly and those with underlying health conditions. While a portion of other patients had mild cases, many, including young people, experienced long illnesses that could permanently scar lung tissue. Twenty percent of those infected between ages 20 to 44 also required hospitalization, with four percent requiring ICU advanced care.
Treating Covid-19 proved to be resource intensive, with many patients requiring high levels of care, including intubation and artificial ventilation. In Italy and other places, hospital intensive care units quickly filled to capacity, and heath care workers (many working without adequate personal protective equipment) were forced to make life and death decisions about the allocation of ventilators and other resources.
By September, an antiviral medication, Remdesivir, was approved in the United States for treating hospitalized cases of COVID-19. The drug was not a cure, but it showed evidence of shortening the course of illness and reducing the risk of severity. Inexpensive and easily available steroids were also shown reduce deaths in COVID-19 patients who were hospitalized with "severe and critical" illness, according to data from clinical trials conducted by the WHO.
The controversial drug Hydroxychloroquine (or an alternate form, Chloroquine) continued to be in use in some countries to treat COVID-19. For a short time it was tried in the U.S., but limited FDA approval was subsequently withdrawn after data from large randomized clinical trails indicated the risks of taking the drug outweighed any statistically discernable benefit.
The outbreak and general course of the pandemic
The initial outbreak of a novel coronavirus with an R-naught significantly greater than one (R0 >1) prompted Chinese officials to institute the largest quarantine in history, with restrictions on the movements of tens of millions of people. China consistently expanded the areas of quarantine, closing schools and halting public transportation and movement into and out of quarantined areas. This required a massive dedication of resources, as Wuhan alone has about the same population as New York City. Despite efforts that lowered China's own case and death counts, containment of the virus failed.
In the early months of the pandemic, Europe, Italy, Spain, and France were especially hard hit, with high numbers of cases and deaths. Even after three weeks of social isolation measures, the United Kingdom reported a high number of cases and deaths. Russia also imposed restrictions. These measures aimed to mitigate the outbreak by flattening the exponential curve in case growth, thus preventing hospitals from being overrun and unable to adequately treat all patients.
Cruise ships and nursing homes proved to be natural environment for the early spread of the virus. Before the outbreak became truly global, a cruise ship named the Diamond Princess, quarantined off Japan, represented the largest outbreak of novel coronavirus cases outside of China. Across the United States, during the first months of the pandemic, about 43 percent of deaths were among residents and health care workers in nursing homes and other long-term care facilities.
By the end of March 2020, the vast majority of schools in America were closed, and the pandemic resulted in the postponement of major sporting events around the world, includingcx the 2020 Olympics (set to be held in Japan) until 2021. Social gatherings were restricted as parks, beaches, and other public spaces closed. Some U.S. states delayed presidential primary elections.
Globally, reports of critical shortages of masks and other protective equipment needed by health workers were common.
By April 2020, almost half the world's population was in some form of quarantine or self-isolation, and epidemiologists continued to emphasize that only social distancing could slow the spread of the virus. By mid-April, the outbreak in the United States spanned all states but was most intensely focused on New York City and surrounding areas. By June, the state of New York reported nearly 25,000 dead from COVID-19 and by September the state attributed more than 32,500 deaths to COVID-19.
Because of the resulting economic devastation, countries faced escalating pressure to loosen public health restrictions in favor of restarting and rebuilding economic activity. Economists warned of a looming and serious global economic recession. The International Monetary Fund (IMF) forecast the most severe global economic depression since the 1930s. In the U.S., by May 2020, more than 40 million workers had lost their jobs.
To mitigate economic losses, the United States Congress passed a bipartisan bill to initially provide $8 billion in emergency funding to combat the coronavirus outbreak. In late March, the U.S. passed another bill, the largest spending bill in its history, allocating approximately 2 trillion dollars to help fight the outbreak and stimulate an economy largely shut down by the pandemic. The emergency funding provided means for the manufacture and distribution of test kits, ventilators, education programs, and protective equipment. It also provided funds for additional research on treatment and vaccine development.
Six months into the pandemic, case counts and deaths varied worldwide as the pandemic began to exhibit wave-like spikes of cases and deaths in some regions while declining in others. In the United States, after a brief decline in cases and deaths that resulted in a loosening of prevention measures in many states, cases and deaths began soaring, again, to record highs throughout the summer months.
Due to rapidly evolving knowledge about the SARS-CoV-2 and COVID-19 shifts in recommendations by health care officials and regulations imposed by governments, in many areas, led to a loss of public confidence, open skepticism, defiance and politicization of issues related to the pandemic. For example, during the first few months of the pandemic in the U.S. the CDC recommended that people not wear facemasks unless they showed symptoms. In part this was due to the fact that the nature of asymptomatic transmission was not fully known and also because facemasks were in short supply for at least the first five months of the pandemic. Ultimately, scientific studies showed masks significantly reduced public transmission.
While most masks were ineffective barriers to the microscopic virus itself, they reduced the range of projection of contaminated vapor and droplets expelled by the wearer when breathing and speaking. Some studies showed that the amount of virus encountered correlated strongly with the severity of subsequent symptoms and the severity of disease outcomes. If that hypothesis proves out in further research, then wearing masks, even masks incapable of stopping individual viral particles, might also provide some direct benefit to the wearer by reducing the viremic load (the amount of virus) encountered.
Prevention, treatment, and vaccine development
As of September 2020, at least 92 potential vaccines were in various stages of development and testing. Some countries, including China and Russia, were administering unproven vaccines to essential personnel, but those vaccines had not undergone the full spectrum of clinical testing for safety and efficacy as required in the United States and most western countries. While Russia claimed to have developed a vaccine, dubbed Sputnik-5, in August 2020, it failed to published data for international peer review by other scientists. Moreover, Russia's initial test group of 76 subjects was widely criticized as being too small to provide statistically significant results. Most clinical trial in the United States and Europe test 10,000 to 40,000 people before trying to draw conclusions as to whether a vaccine is effective and safe.
Early vaccine candidates included a potential ribonucleic acid (RNA) based vaccine. The candidate mRNA-1273 vaccine is not made from the virus itself, but rather a short segment of genetic code copied from the virus RNA that can be reproduced in a laboratory. Although the segment cannot cause disease, the hope is that, once injected, the segments can stimulate a lasting immunity-conferring immune response.
Without a vaccine to prevent COVID-19, the best way to prevent illness is to avoid exposure. The CDC recommends the following everyday preventative actions to help prevent the spread of respiratory diseases, including COVID-19:
- Practice social distancing (staying 6 ft—approximately 2 meters—away from other people not in your isolation cohort)
- When in public, wear a mask to avoid distribution of potentially infectious droplets. The CDC emphasizes that wearing a mask protects others and lessens community transmission especially as many people are infectious before they show symptoms.
- Avoid close contact with people who are sick.
- Avoid touching your eyes, nose, and mouth.
- Stay home when you are sick.
- Cover your cough or sneeze with a tissue, then throw the tissue in the trash.
- Clean and disinfect frequently touched objects and surfaces using a regular household cleaning spray or wipe.
- Wash your hands often with soap and water for at least 20 seconds, especially after going to the bathroom; before eating; and after blowing your nose, coughing, or sneezing. If soap and water are not readily available, use an alcohol-based hand sanitizer with at least 60 percent alcohol. Always wash hands with soap and water if hands are visibly dirty.