Review

, Volume: 15( 2) DOI: 10.21767/0974-7532.1000153

COVID-19: Morphology, Characteristics, Symptoms, Prevention, Clinical Diagnosis and Current Scenario

*Correspondence:

Mukesh Meena
Department of Botany
Mohanlal Sukhadia University
Udaipur, Rajasthan, India
Tel: +91- 9667720689
E-Mail: mukeshmeenamlsu@gmail.com

Abstract

There are different types of viruses are found in nature which cause infection in humans and other animals, some causing severe illness and others not. A unique coronavirus termed Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) was isolated from lower respiratory tract sample as the causative agent. The recent outbreak of contagions with SARS-CoV-2 is termed Coronavirus Disease 2019 (COVID-19) by the World Health Organization (WHO). At present, whole world is struggling with COVID-19 disease. COVID-19 quickly spread into at least 215 countries and exterminated more than 300,000 persons by May 15, 2020. This is the time to exercise restrains and caution. Whole world’s many governments, scholars and scientists are engaged for discover the proper treatment until we find proper and right treatment for it we have to be careful to avoid infection. This review article includes characteristics of COVID-19, current scenario of disease, causes and symptoms of disease and how to prevent from its infection.

Keywords

Coronavirus; SARS-CoV-2; COVID-19; Pandemic; Infection

Abbreviations

SARS-CoV-2: Severe Acute Respiratory Syndrome Coronavirus-2; COVID-19: Coronavirus Disease 2019; WHO: World Health Organization; SARS: Severe Acute Respiratory Syndrome; CoV: Corona-Virus; SARS-CoV: Severe Acute Respiratory Syndrome-Linked Virus; MERS: Middle East Respiratory Syndrome; R⁰: Basic Reproduction Number; CI: Confidence Interval; HE: Esterase and Hemagglutination; ACE 2: Angiotensin-Converting Enzyme 2; RNA: Ribonucleic Acid; CDC: Europe Center of Disease Control; OSCAR: Oxford Suzhou Centre for Advanced Research

Introduction

The novel SARS-CoV-2 corona virus that emerged in the city of Wuhan, Hubei Province, China, on dated December 8^th 2019 and has since caused a large scale COVID-19 pandemic and spread to more than 215 other countries or territories or areas. Corona virus is a type of infected virus which was discovered as novel agent on dated 9^th January 2020 [1], with a unique history of confirming the first case of human infection due to avian influenza A H5N1 in 1997 [2] and Severe Acute Respiratory Syndrome (SARS)-associated Corona-Virus (CoV) in 2003 [3].

In spite of the determination to break the transmission of COVID-19, the contagion spread all over China, and in January 2020, cases were reported in Japan, Thailand, and South Korea [4,5]. Within less than 3 months since the detection of the unidentified pathogen, the infection extent to at least 114 countries and caused over 4,000 demises. In India, the first case of the COVID-19 was identified on 30 January 2020, and as of 15 May 2020, a total of 85,940 confirmed cases leading to 2,753 deaths has been reported.

Two unique strains of coronavirus have leaped species from animal to human, spread by human-to-human transmission, and caused severe acute respiratory syndrome leading to high fatality rate in the past 2 decades [6]. Severe Acute Respiratory Syndrome-Linked Virus (SARS-CoV), hitherto unidentified coronavirus traced to horseshoe bats in southern China, caused 8,096 confirmed cases and 774 demises in 29 countries from November 2002 to July 2003 [7]. Now a day’s, the whole world is suffering from COVID-19 disease. This article reviews the characteristics of COVID-19, causes, symptoms, preventions and current scenario of the disease. TABLE 1 briefly describes distinctive features of SARS-CoV-2 in comparison to SARS-CoV [8].

Table 1: Differences in epidemiological characteristics of SARS (SARS-CoV), MERS (MERS-CoV), and COVID-19 (SARS-CoV-2).

Morphology and Genome Sequence of COVID-19

Coronaviruses are enveloped, pleomorphic or spherical particles, 150 nm to 160 nm in size, linked with constructive single stranded RNA, unsegmented, nucleoprotein, capsid, matrix, and surface glycoprotein (S-protein) (FIG. 1). Significant viral proteins are nucleocapsid protein (N), membrane (M), spike glycoprotein (S), and envelope small membrane protein (E). TABLE 2 showed structural proteins of COVID-19 and their functions. COVID-19 varies from further coronaviruses by encoding a supplementary glycoprotein that has acetyl Esterase and Hemagglutination (HE) properties [9,10].

Table 2: Structural proteins of COVID-19 and their functions.

Evaluation of the genome arrangement of the COVID-19, SARS-CoV, and MERS-CoV revealed that COVID-19 has enriched sequence uniqueness with SARS-CoV than the MERS-CoV6. The COVID-19 amino acid arrangement differs from former coronaviruses with polyprotein and S-protein. S-protein has two subunits with single subunit binding directly to the host receptor assisting the entry of virus into cells. The RNA binding domain of the S-protein in COVID-19 has superior homology with SARS-CoV. Studies suggest that the human receptor for COVID-19 might be Angiotensin-Converting Enzyme 2 (ACE 2) [11,12]. Also, other coronaviruses comprising SARS-CoV advantage appearance into human cells through ACE 2. It has been noted that specific CoV do not need to have the full ensemble of structural proteins to make virons, highlighting that certain proteins may be dispensable or compensated by the function of non-structural proteins [13,14].

Characteristics of the Corona Virus (SARS-CoV-2)

The coronaviruses have five vital genes which are for four structural proteins (N, E, M, S) and for viral replication/transcription (Ribonucleic Acid (RNA) dependent RNA polymerase, RdRp). The genome organization is 5’-RdRp-S-E-M-N-3’. This gene order of coronaviruses is highly conserved [15]. Complete genome sequence of SARS-CoV-2 reveals that it is a novel beta coronavirus distinctive from SARS-CoV [16]. The nucleotide sequence of SARS-CoV-2 revealed 79.0% and 51.8% uniqueness with SARS-CoV and MERS-CoV, correspondingly and it is very closely linked to bat-SARS-identical coronavirus (bat-SL-CoVZC45) with 87.6%-89% identity [17,18].

Based on the phylogenetic analysis, the Coronaviridae Study Group of International Committee on Taxonomy of Viruses named the virus SARS-CoV-2, on 11 February, 2020 [19]. On the similar day, the WHO termed the disease initiated by the novel Coronavirus Disease 2019 (COVID-19), in arrangement with WHO best practices for naming of new human infectious disease [20]. Based on the virus genome sequencing data, bats are presumed to be the reservoir of SARS-CoV-2, but the transitional hosts are not identified till date. SARS-CoV-2 enters into the host cell through binding its spike proteins, which regulate host tropism, to host cell receptors [21,22]. Preliminary investigations had proposed that SARS-CoV-2 might share a host cell receptor with SARS-CoV, because the 2 strains have equivalent receptor-binding protein configurations. Consecutive studies revealed that SARS-CoV-2 binds to ACE 2 as SARS-CoV does [23,24]. SARS-CoV-2 was first isolated from a bronchoalveolar lavage sample [16] and RNA of the virus was also detected in nasopharyngeal and throat swabs as well as blood, stool, urine, and saliva [25,26].

Symptoms of COVID-19

Symptoms of this virus are like pneumonia. Potency of SARS-CoV-2 may be mild, moderate or severe based on the strength of the immune system of the infected individual. A certain pattern in the bulk of cases tends to reflect the scientific improvement of the disease. In a proportion that has yet to be known, after around a week, infected person health consequences have unpredictably deteriorated, as respiratory failure has weakened promptly. The life-threatening respiratory failure situations and medical requirements of sepsis and septic shock should be taken seriously [27]. Patients with uncomplicated (mild to moderate) illness generally have signs that comprise slight fever, arid cough, sore throat, fatigue, stomach aches, respiratory irritation and malaise, although testified dyspnea in patients were asymptomatic [28]. Nonrespiratory signs for instance diarrhea are significant to recognize comparative to earlier HCoV infections. Adequate pneumonia respiratory signs for example cough and shortness of breath (or children’s tachypnea, etc.) were reported for patients in some cases [29]. Life-threatening pneumonia fever is initiated by substantial illnesses, respiratory depression or hypoxia (SpO2<90% in the room). Fever is constant with extreme pneumonia [30]. However, fever signs supposed to be properly predictable as slight or occasionally missing, even in thrilling cases of the disease. In kids, cyanosis can occur. The illustration includes a psychiatric disorder, and radiological terminology is used to abolish difficulties with clinical and ventilator supplies that are required for this diagnosis [29]. The extent of hypoxia in several forms of ARDS is different [31]. Moreover, sepsis is a serious organ dysfunction owing to dysregulated host responses to doubted or recognized organ dysfunctions [32]. The clinical depictions of patients with SARS-CoV-2 and sepsis are mainly severe, with an extensive assortment of signs, symptoms (cardiac disorders, for instance extreme dyspnea and hypoxemia, acidosis, altered mental state, abnormal vomiting, and efficient organ variations), and signs of multi-organ shock accessible as hyperbilirubinemia laboratory results [31].

Identify fit symptoms of corona virus infection are following: headache (14%), runny nose (5%), sore throat (14%), fever (88% cases), vomiting (5% cases), shortness of breath (19% cases), joint pain (15%), fatigue (38%), chills (11%), diarrhea (4%), phlegm (33%), dry cough (68%), confirmed by World Health Organization (reports based on 56, 000 lab cases) database.

Clinical Progression and Diagnosis

The mission through Google dataset for SARS-CoV-2 diagnosis (TABLE 3) concluded in five guidelines, webpages with links and recommendations for public knowledge (WHO, Europe Center of Disease Control (CDC), US CDC, US FDA). The incubation phase for COVID-19 is believed to be inside 14 days following exposure, with most cases happening roughly four to five days after acquaintance [33,34]. In an investigation of 1099 patients with affirmed symptomatic COVID-19, the median incubation time period was four days (interquartile run two to seven days) [18]. Utilizing information from 181 openly revealed, affirmed cases in China with recognizable presentation, one displaying study evaluated that side effects would develop in 2.5 percent of contaminated people inside 2.2 days and in 97.5 percent of infected people inside 11.5 days [35]. The median incubation period in this investigation was 5.1 days.

Table 3: SARS-CoV-2 diagnosis systematic assessment results.

COVID-19 shows with a wide clinical range extending from asymptomatic patients to septic shock, multiorgan brokenness and fatal pneumonia [36]. The rate of asymptomatic infection is hitherto to be defined, since utmost initially asymptomatic infections finally turned symptomatic. COVID-19 is organized reliant on the seriousness of the appearance [36]. The infection might be characterized into mild (no or mild pneumonia; 81%), moderate (mild pneumonia), serious (with dyspnea, hypoxia, or>50 percent lung involvement; 14%), and critical (eg., with respiratory failure, shock, or multiorgan dysfunction; 5%) [37]. The most widely recognized manifestations of patients incorporate fever (98.6%), exhaustion (69.6%), dry cough, and diarrhea [37]. The entire case fatality rate was 2.3%; no deaths were testified among noncritical cases. Symptomatic infection in children appears to be relatively infrequent; when it arises; it is usually mild, although severe cases have been stated [38,39].

Fatality rate of COVID-19 in China is 3.8%; the fatality rate in Wuhan City is 5.8%, in contrast to that of 0.7% in the rest of mainland China. Risk factors of extreme pneumonia or demise incorporate ages 60 or above, and clinical comorbidity, for example, hypertension, cardiovascular sickness, diabetes mellitus, incessant aspiratory infection or threat. Research facility trial of the affirmed COVID-19 cases appeared leukopenia, lymphopenia, mild raised C-receptive protein.

In the meantime, SARS-CoV contamination generally presents with fever. The disease starts with fundamental complaints including myalgia, chills, or fatigue, trailed by dry cough and dyspnea following a couple of days to seven days. Symptoms of upper respiratory tract contamination, for example, rhinorrhea or sore throat are uncommon. Watery looseness of the bowels might be gone within 10%-25% patients in later course of the malady. Serious consideration was required in 20%-30% of patients, with 10% casualty rate. In ages more established than 60 years, casualty rate was half. Death mostly occurred in the third week from the beginning of symptoms.

How the Corona Virus Spreads?

The human Corana Virus (COVID-19) usually spreads from one person to another. It is also transmitted through aerosol [40]. There are several ways which spreads this virus in the environment and person to person. These are ways following: open air coughing and sneezing; close personal contact such as touching or shaking hands; virus is transmitted through air, surface, environmental and personal protective equipment’s [41]; touching a narrow object or surface, then touching nose, mouth or eyes without washing hands; use of infected thing like vegetable and other food items.

Prevention of Corona Virus

Preventive estimates must concentrate on improving disease control conventions, self-isolation, and patient disengagement during the arrangement of clinical consideration. The WHO has prompted against close contact with patients, livestock, and wild animals. Patients and the overall population must cover coughs and sneezes to aid preclude aerosol transmission. Regular hand washing with disinfectant and water is likewise required. As a substitute measure, hand sanitizers can also be utilized. Immunocompromised people are encouraged to maintain a strategic distance from open social occasions. Crisis medication divisions must apply severe cleanliness measures for the control of diseases. Medicinal services faculty must utilize individual defensive equipment for example, face masks like N95 masks, FFP3 masks, gowns, eye assurance, gloves, and outfits [42].

The WHO and similar types of organizations have made the following broad-spectrum guidelines: always clean hands with soap and water or alcohol-containing hand bars; when coughing and sneezing, cover the nose and mouth with a tissue or bent elbow; avoid making close contact with people who have cold or flu-like symptoms; use the mask and after using it dispose by burning of buried; avoid going to public places and crowds; stop hazardous field touch or wildlife interaction; do not bring food items made out of the house; fortify the execution of severe cleanliness measures to stay away from and oversee diseases, especially in the emergency medicine divisions; To keep taking more fluids [43,44]. If having fever, cough and difficulty in breathing, contact the doctor as soon as possible. Be aware of the important information related and follow the advice given by doctor. There is one example of prevention is that Indian government put one day ‘JANTA’ curfew on dated March 22, 2020 for the same.

Current Scenario

According to WHO, it is pandemic disease and found 203 countries, areas or territories and till May 15, 2020 total confirm cases 4,628,821 and confirmed deaths are 308,654 [45]. In India, total 85940 cases are confirmed out of 2753 death and 30258 get recovered till May 15, 2020. The highest confirmed in Maharashtra state which is 29100 and deceased 1068 [46]. Here, we presented the worldwide report of confirmed cases and deaths by country, territory, or conveyance.

Confirmed Cases and Deaths by Country, Territory, or Conveyance

The coronavirus COVID-19 is affecting 213 countries and territories around the world and 2 international conveyances: the Diamond Princess Cruise ship harbored in Yokohama, Japan, and the Holland America's MS Zaandam cruise ship. The day (May 15, 2020) is reset after midnight GMT+0. TABLE 4 showing the report of coronavirus cases overall the world.

Table 4: All countries report of coronavirus cases (Data obtained from May 15, 2020).

Conclusion

The COVID-19 pandemic is scattering transversely the world at an alarming frequency. It has caused more contagions and demises as compared with SARS or MERS. Based on R0 values, it is considered that SARS-CoV-2 is more infectious than SARS or MERS. Aging and immunocompromised patients are at the extreme threat of mortality. The prompt extent of disease permits intense investigation and quarantine protocols to preclude further transmission. Till date, no chronic medication or vaccine has been developed. Modern treatment approaches are intended at symptomatic care and oxygen therapy. In future, prophylactic vaccination will be compulsory for the imminent prevention of COV-associated epidemic or pandemic.

Acknowledgements

Authors would like to thank Department of Botany, Mohanlal Sukhadia University, Udaipur, Rajasthan, for providing necessary facilities. Authors are also thankful to online available sources, organizations like World Health Organization; Ministry of Home Affairs, Government of India, etc.

Conflict of Interest Statement

No potential conflict of interest relevant to this article was reported.

Funding Sources

There is no funding source available.

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