In 16th century, a (1) famous physician and astrologer, Nostradamus predicted that “‘…great calamity, Through the Lands of the West…plague and captivity’” forecasting a cataclysm due to a disease. Moreover, in a 2015 TED conference, Bill gates (2) asserted that, “If anything kills over 10 million people in the next few decades, it’s most likely to be highly infectious virus rather than a war.” Over the past decades, the most catastrophic pathogens have been the viruses. Undoubtedly, human history has witnessed three capricious and devastating diseases causing mass destructions to the mankind. The deadliest was the 1918 ‘Spanish Flu’ killing over 50 million masses. Followed by the H1N1 influenza of 2009 infecting people across 213 countries and then the West African Ebola virus outbreak of 2014. (3) (NCBI BOOK). Contemporarily, the humanity is reliving the past because of the Covid-19 havoc.
Amidst the New year 2020 celebrations on December 31, 2019, the Chinese government alerted the WHO (World Health Organization) about a novel (new) infection spreading in a Seafood Market at Wuhan, China. On January 11, 2020, 61-year old man died, and the number of cases were increasing at alarming rates. Later, the WHO estimated the disease’s potential to become a ‘Global Emergency’ and declared the disease as ‘Covid-19’ or a Coronavirus Disease 2019 caused by ‘Coronavirus’ now called SARS-CoV-2. On March 11, 2020 The WHO declared Covid-19 as a ‘pandemic’, defined as a novel (new) disease emerging globally; stating 1,18,000 cases worldwide and more than 4000 deaths.(4) (YouTube video) Following month, the number of cases incremented to l,13,53,361 and 79,235 deaths reported by the WHO on April 8, 2020. (5) With escalating death toll and undiscovered treatments till now, need-of-the-hour is to understand the Coronavirus pathogenicity (science) and the COVID-19 symptoms.
Though it is challenging to understand the science of Coronavirus virus,exploring the pandemic at different levels is significant. The initial step is the recognition of genealogy (ancestry) and the origin of the virus called as etiology. Then, epidemiological investigation of the disease dispersal is fundamental. Further, the pathogenetic examination of the infection mechanism ends up with vaccine development. The Coronavirus science can be understood by studying the underlying etiology, epidemiological factors and viral pathogenesis successively.
The discovery of the lineage and origin of the coronavirus is the key approach to understand the COVID-19 science. Importantly, this virus is not an unprecedented pathogen, conversely, a new form of pre-existing viruses infecting the respiratory tracts of the organisms. Speciffically, it belongs to Corornaviridae family of highly infectious coronaviruses classified as: AplhaCoV, BetaCoV, DeltaCoV and GammaCoV each affecting different genera and species. As this SARS-CoV-2 infects humans, its genus is BetaCoV which includes the viruses infecting mammals.(Guo et al., 2020) (6) It typically infects the respiratory system of the humans, thereupon called ‘Severe Acute Respiratory Syndrome’ Coronavirus 2 (SARS-CoV-2) where ‘2’ represents the second form of SARS virus that ever-infected humans after SARS-CoV.
Presently, it is the third extremely contagious Coronavirus after SARS-CoV and MERS-CoV. (Guo et al., 2020) (6) However, the source of the novel SARS-CoV-2 is still under investigation. Nevertheless, some experimental studies suggest, “…the genome sequence of SARS-CoV-2 is 96.2% identical to a bat CoV RaTG13,… Based on virus genome sequencing results and evolutionary analysis, bat has been suspected as natural host of virus origin, and SARS-CoV-2 might be transmitted from bats via unknown intermediate hosts to infect humans” as “…SARS-CoV-2 could use angiotensin-converting enzyme 2 (ACE2), the same receptor as SARS-CoV , to infect humans.” (Guo et al., 2020) (6) Indeed, this COVID-19 is a pandemic caused by a slightly dissimilar form of pre-discovered Coronaviruses with origin still under investigation.
The determination of the SARS-CoV-2 origin is followed by analyzing the COVID-19 distribution patterns including transmission and the infection trajectory. COVID-19 is a communicable disease. A video by Science Animations on March 4, 2020, explained, “it is a contagious viral infection spread through inhalation or ingestion of viral droplets. As a result, coughing and sneezing and touching infected surfaces are primary sources of infection.” Consequently, this virus is infecting a human population extensively, affecting various age groups, communities and individuals with various health conditions. Furthermore, in the e-book; Features, Evaluation and Treatments Coronavirus (7) (COVID-19), the author Casella et. al asserted that “…on average, each patient transmits the infection to an additional 2.2 individuals.” (2020) It can be concluded that it is spreading as fast as the common cold. Additionally, animal-to-human transmission is assumed as the first dissemination and the following cases observed are mostly owing to community transmissions. (Adhikari et al., 2020) (8). Overall, this virus is quite contagious transmitting through aerosols and growing tremendously.
The infection distribution can help to understand the pathogenic process (mechanism) of the SARS-CoV-2. Before SARS-CoV-2 infection mechanism, it is necessary to understand the structures of viruses. In general, the viral structure is uncomplicated; a DNA or RNA strand as a genetic material which is enclosed by two protein coats with spikes often called Receptors. The genetic material uses the host (infected cell) machinery to generate thousands of virus copies. The protein coats protect the hereditary content and merge with the host cell membrane when invading the host cells. The spikes attach with the host’s membrane receptors like a ‘lock and a key’, followed by endocytosis which is “Virus entry through receptor interactions and vesicle formation” (S. Cockburn, personal communication, February 13, 2020) (10). The SARS-CoV-2 have membrane spikes- Corona with S glycoproteins which bind to the ACE2 (Angiotensin Converting Enzyme 2 Receptor) receptors on the epithelial or membrane cells of the human respiratory tract. This arcane binding action still unknown to the scientists causing a delay in vaccine creation. Nevertheless, the SARS-CoV-2 then uses the human cells ribosomes encode for the protein structures for producing new viruses. These viral cells then attack the alveoli or the air sacs in the lungs where the gas exchange with blood takes place. Consequently, the alveolar cells inflame or swell due to fluid-filling and make the breathing process difficult. Thence, pneumonia and shortness of breath are the main symptoms. To conclude, the pathogenic mechanism of SARS-CoV-2 is like that of other viruses, but the binding action is still ambiguous to the human erudition. (11)
Although the complex science of the COVID-19 is imperative, but what makes more sense to the public is awareness of symptoms. The timely detection of symptoms leads to accurate disease tracking, saving the lives of both, the infected and the healthy persons. However, understanding the signs is Sisyphean as humans can be symptomatic, asymptomatic or paucisymtomatic. Therefore, to ameliorate the notions, the symptoms can be understood in three steps: symptom classification, symptom chronology and symptomatic groups.
The categorization of the COVID-19 manifestations is significant in diagnostics and determining the patient’s condition. Based on the disease severity levels, the Chinese CDC (Chinese Centre for Disease Control and Prevention) classified the symptoms into “four stages: Mild, Moderate, Severe and Critical.” (as cited in Cascella, 2020) (7) The mild symptoms include the URTI (Upper Respiratory Tract Infections) like dry cough, sore throat, cold, headache, nasal congestion and slight fever whereas breathlessness and cough are moderate symptoms. Severe symptoms like pneumonia, hypoxia (lack of oxygen in the body) leading to cyanosis (bluish hands and fingers), dyspnea (breath shortness) or even tachypnea (faster breathing rate) indicates grave medical condition. The ARDS which is Acute Respiratory Distress Syndrome; a respiratory failure or even a sepsis shock which is “…a life-threatening organ dysfunction,” defined by Singer et al., “caused by a dysregulated host response to suspected or proven infection, with organ dysfunction.” are included in Critical symptoms with low recovery chances. (Cascella, 2020) (7). To recapitulate, the understanding of the symptoms and their four stages can help in timely identification and treatment of the COVID-19 disease.
Likewise, symptom classification, it is inevitable to carefully evaluate the symptom sequences with respect to time. Usually, it can take between 2-14 days for the first symptom like fever to arrive after being infected with coronavirus. In fact, WHO and CDC joint mission (12) stated that approximately, 88% of the COVID-19 patients have fever initially. Meanwhile, some gastrointestinal symptoms, diarrhea, nausea, vomiting and abdominal discomfort may appear before respiratory problems begin. Next, lung and tracheal inflammation cycle commences due to damaged tissues causing dry cough, shortness of breath and phlegm production along with fatigue, sore throat, a runny nose, headache, muscle pain and chills.
Normally, recovered patients get discharge from the hospital after two and a half weeks. By the day five, the mild cases clear up but patients with pre-existing medical conditions have trouble in breathing leading to need of hospitalization till the seventh day. Subsequently, patient is prone to ARDS requiring advanced life support in the Intensive Care Units (ICU). Eventually, the patient completely depends on supplemental oxygen and mechanical ventilation for survival. If the lungs are quite inflamed and are unable to deliver any oxygen into your bloodstream, death is closer. Gradually, such patients survive generally for only 14-19 days of infection. Even if a patient survives, a permanent lung damage is certain. Thus, the survival battle with COVID-19 lasts between 14 days to roughly three weeks with mild to endless sufferings. (YouTube) (4****)
Finally, symptom sequencing is followed by identification and distinction of the symptomatic vulnerable groups for exploring the COVID-19. Till now the overall patients’ ages range from 2-72 years and most of them have been males; the reason behind higher male percent is still unresolved. There are three most symptomatic and susceptible sets to the Covid-19. Firstly, the elderly is the most sensitive group. A recent study by researches revealed that the adult people between 25 to 89 years of age are more prone to the disease than the children and the mean death age observed to be 75 years. (Adhikari et al., 2020) (9) Second most susceptible group is the people with chronic illnesses. Dr. Patrick Soon-Shiong, the executive chairman of the Los Angeles Times, reasserted the CDC data that people with pre-existing cardiovascular diseases and chronic respiratory illness have 10.5% and 6.3% risk of being infected respectively. Los Angeles times (13), (2020)
Moreover, diabetic patients, people undergoing chemotherapy for cancer treatments and suffering from high blood pressures are equally disposed. Weak immune system is the root-cause. If the immunity is not strong enough, the virus cell continues to infect the lungs, killing the epithelial cells and hence causing a long-term damage to the organ. Thirdly, health care providers are the at-risk-population. Owing to high transmission rate, they can acquire Covid-19 as a nosocomial infection- the infections acquired at the hospitals. Even regular and direct exposure to the contaminated can raise serious health issues in the physicians and care takers of the infected. “As of 20 February 2020, there were 2,055 COVID-19 laboratory-confirmed cases reported among HCW from 476 hospitals across China.” reported by the WHO-Joint Mission on Coronavirus Disease (12) 2019. Hence, the old, unwell and exposed workers have a high propensity of catching the Coronavirus due several reasons.