COVID-19: A Global Emergency

The most common causes of death due to COVID-19 are related
to the lungs, kidneys, and the heart. Severe COVID-19 can cause...


Introduction
The most common causes of death due to COVID-19 are related to the lungs, kidneys, and the heart. Severe COVID-19 can cause heart failure, regardless of the patient's past cardiac history [1].
Phylogenetical analysis revealed that SARS-CoV-2 is a lineage B β-CoV [2,3]. CoVs have at least four structural proteins: Spike (S), Nucleocapsid (N), Membrane (M), and Envelope (E). S facilitates host attachment, entrance, and virus-to-cell membrane fusion during infection. S glycoproteins foster entry into cells and SARS-CoV-2 S utilizes the angiotensin-converting enzyme II (ACE2) to enter cells [4,5]. Viral infectivity relies on interactions between the virus envelope and components of the host cell's plasma membrane. It has also been demonstrated that certain molecules can decrease the infectivity of some CoVs [6]. COVID-19 can be regarded as an issue of One Health, which is an approach that attempts to strategize coordinated efforts of multiple disciplines, including environmental health and environmental surveillance [7]. The relationship between COVID-19 cases and meteorological factors in 30 Chinese provincial capitals was studied by scholars.
A daily dataset was compiled, including confirmed cases, absolute humidity, diurnal temperature range, ambient temperature, and migration scale index for every provincial capital. Meteorological factors were discovered to have independent effects on the transmission of the disease, while weather with a low humidity, a low temperature, and a mild diurnal temperature range facilitates COVID-19 transmission [8].
Infectious diseases are rapidly spread by national and international travel. Respiratory droplets infected with viral material can cause surface contamination when the virus settles on hard surfaces such as plastic, cardboard, metal, etc., called fomites, and is often present on various sites and subjected to touch many times daily, indicating a possible risk in some airport sites, schools, businesses, etc. Among tested surfaces, plastic trays in the security screening area seemed to have the greatest probability of risk and managing the risk is nearly impossible as infection from touching these surfaces is almost unavoidable for boarding passengers.
Symptomatic or asymptomatic respiratory tract infection of passengers infected with COVID-19 could be frequent with possible transmission to other passengers via multiple transmission modes (such as droplet and contact) during travel or when arriving at the destination [9]. The main purpose of this paper is to explore COVID-19, including its features, progress in therapeutics, testing, and challenges facing healthcare providers and experts. Many people are unaware of the risk of infection, in part due to some similarities to other viral diseases such as influenza, MERS, SARS, and EVD. Some health experts have even gone so far as theorizing that prior exposure to SARS has increased immunity in some populations. Therefore, these viral diseases are also introduced in comparison with COVID-19. and Prevention (CDC) were caused by H1N1 [10]. The pandemic potential and transmissibility of flu viruses relies on their ability to efficiently replicate, retaining viability when being released from a host with infection and maintaining virility while passing through the environment, and initiating new infection in the next host [11].
Conventional flu vaccines are developed to stimulate neutralizing antibodies against the immunodominant, while inherent limitations including a lack of protection from an antigenically novel pandemic flu and suboptimal protection from rapidly changing seasonal flu viruses. New technology for developing flu vaccines has focused on aiming conserved antigens and stimulating a cross-reactive T cell response [12]. Influenza viruses may also mutate, which can possibly reduce the effectiveness of the vaccines. The efficacy of a flu vaccine may rely on factors such as drift, underlying medical condition, patient's age, and any medications leading to immunosuppression [13]. Next-generation sequencing (NGS) facilitates a more efficient response to the flu, because NGSs can be employed to identify drug resistant mutations in clinical flu virus isolates [14].  [17,18]. The epidemiological features of SARS-CoV-1 at first suggested that SARS transmission was through airborne transmission via large respiratory droplets and but the orofecal route through contact with humans and surfaces contaminated with SARS-CoV-1 cannot be rule out. While most cases were the direct human-to-human transmission through respiratory droplets, other modes of transmission have also been discovered. Fecal shedding in patients with SARS is frequent and has led to an outbreak in Hong Kong. The spread pattern of SARS related to sick patients who travel on airplanes has demonstrated that airborne transmission can also happen during a flight [18,19]. There is no certified vaccine or specific antivirals for SARS. The outbreak of SARS from 2002 to 2003 was controlled using traditional methods, such as patient isolation, travel restrictions, therapeutic treatments, etc. [20].

SARS and MERS
MERS coronavirus (MERS-CoV) enters the human population through indirect or direct contact with infected dromedary camels as well as infected persons [21]. The single-humped, Arabian dromedary camel has been strongly implicated as the MERS-CoV reservoir in which the disease is either asymptomatic or manifested as a mild respiratory infection. High seropositivity rates of MERS-CoV were detected in dromedaries from many African and Arabian countries. MERS-CoV causes a severe respiratory infection, possible renal failure, and potentially multiorgan damage in infected patients [22]. MERS-CoV can also be transmitted through airborne particles; human-to-human transmission occurs primarily through the inhalation of infectious respiratory droplets or via direct contact with an infected patient. Indirect transmission can also occur via contaminated items, e.g., devices, equipment, and surfaces. A large viral load of MERS-CoV was found in the fecal samples of certain types of bats, but the bats tested were different from the types in Saudi Arabia where the MERS outbreak happened [23]. There are no certified antiviral therapeutics or vaccines for MERS and management is chiefly supportive based on the patient's clinical condition [24]. Climate factors affect MERS with an increase in cases from April to August. A low relative humidity, low wind speed, high temperature, and high ultraviolet index can help increase the number of MERS cases. Climate conditions should be assessed in community settings and hospitals, incorporated into policies and guidelines as a source or measure for prevention, and used for the control and elimination of the infection risk [25]. MERS is still in the WHO list of possible major pandemics, and issues regarding pathogenesis, epidemiology, control, and management need to be addressed. A joint international response plan for MERS-CoV is essential for better coordination and collaboration [26].

Ebola viral disease (EVD) is caused by the Ebola virus (EBOVs).
EVD has occurred mainly in West and Sub-Saharan Africa since it emerged in 1976 [27]. However, other countries have experienced outbreaks of EVD because many healthcare workers travel to Africa to assist in caring for patients afflicted with EVD. In the USA, some cases had developed earlier in the prior decade when caregivers traveled home from Africa, infected by patients there. The symptoms of EVD include high fevers, arthralgia, severe fatigue; hemorrhagic manifestations such as oozing and acute bleeding occur in the final stages [28]. Ironically, EVD can also cause a "cytokine storm" and resulting pneumonias and microthrombi disease like SARS-CoV-2.
The "cytokine storm" can result in a fatal respiratory depression, a need for mechanical ventilation, and sequalae associated with the microthrombi. The 2014-2016 outbreak of EVD in West Africa is the largest recorded EVD outbreak [29]. The detection of viral ribonucleic acid based on polymerase chain reaction (RT-PCR) is a standard for testing EBOVs [30]. According to the CDC, EVD is most often 80% fatal. There are no approved therapeutics for EVD or post-Ebola syndrome. Patients in treatment can get discouraged due to the low survival rate of EVD and because EVD carries such a risk of contact infection and has such a low survival rate, healthcare workers are also reluctant to take care of patients with EVD. There has been a considerable amount of research work conducted in the development of vaccines and antivirals or antibody preparations [31]. Micronutrient supplementation has also been suggested for the care of EVD. Early supplementation of multivitamins can help lower overall mortality. An ordinary component of supportive care for EVD is micronutrients. When there is a micronutrient deficiency, international guidelines call for supplementation which includes taking multivitamins [32].

SARS-CoV-2 and Disorders Due to COVID-19: It has been
theorized that SARS-CoV-2 was possibly transmitted to humans from bats or an undecided intermediate animal host [33]. It is 96% identical to a bat coronavirus at the whole-genome level [34]. Its viral pathogenesis has not been confirmed, but sequencebased analysis has indicated that bats should be a key reservoir.
Studies have shown that SARS-CoV-2 utilizes the ACE2 as a cellular entry receptor [2,3,35]. COVID-19 can lead to the respiratory and systemic disorders shown in Figure 1 [36].

Compared to Other Viral Diseases
There are some similarities and distinct comparisons between COVID-19 and other viral diseases such as influenza, SARS, and MERS. Table 1 [37] lists the incubation and virus family of each viral disease. Differences between MERS-CoV, SARS-CoV-1, and SARS-CoV-2 in some epidemiological features are shown in Table   2 [38]. R 0 is the basic reproduction number and it is also called the basic reproductive ratio. Clinical data collected from 31 provinces in China indicate that SARS-CoV-2 and SARS-CoV-1 have some common clinical features, which are shown in Table 3 [39]. It is noteworthy that only 43.8% of patients had a fever on initial manifestation.

Infection and Spread of COVID-19
Age and the presence of comorbid illnesses increase the risk of death among patients with COVID-19 [40].  Personal Protective Equipment (PPE) for medical professionals in the front line [44]. It is necessary to estimate the serial interval that is the period from the illness onset of a primary case to that of a secondary case. This helps understand the virus transmission and the turnover of case generation. The serial interval of COVID-19 is close to or less than the median of its incubation value, suggesting that the infection of SARS-CoV-2 results in a rapid transmission cycle. An estimate of the median of the serial interval of COVID-19 is four days. A considerable ratio of secondary transmission could happen prior to the illness onset. The serial interval value of COVID-19 is also less than that of SARS [45].

Testing of COVID-19
An initial screening for COVID-19 is often used and an b) The detection rate is low if the viral load is low, which leads to a false-negative result.
c) The supply of reagents often does not meet requirements. if not before.  Immunotherapy is an effective therapeutic option of intervention against COVID-19. Primary approaches, for example, utilizing convalescent plasma therapy and immunoglobulins have achieved better clinical effects for patients with COVID-19 [48].
Human coronaviruses (HCoVs), for example, SARS-CoV-2, lead in global pandemics. There have been no certified drugs developed to work against novel SARS-CoV-2. Drug repurposing is a strategic approach to effective drug discovery based on available drugs.
There are currently 16 prospective repurposable anti-HCoV drugs (e.g., sirolimus, mercaptopurine, and the hormone melatonin) have been prioritized based on the network proximity analysis of drug targets [49]. Mutations of SARS-CoV-2 have occurred naturally and easily, however, theories are that while the SARS-CoV-2 is more contagious and easier to spread, its mortality rate has decreased.

Discussion
Since coronaviruses may have frequent recombination and rapid mutation, will these kinds of activities produce novel strains with increased pathogenicity and transmissibility? What is the role played by point mutation and recombination during the evolution of SARS-CoV-2? [53]. The origin of this novel CoV deserves deep study or investigations and some important issues need to be addressed: a) The molecular mechanism of the inter-species transmission of SARS-CoV-2 b) The similarities as well as distinct features of this mechanism compared to MERS-CoV and SARS-CoV-1 [53].
Platelet count is an easily available and simple biomarker that is independently related to a risk of mortality and disease severity in an Intensive Care Unit (ICU). A low platelet count is related to an increased risk of mortality or severity of COVID-19 patients; therefore, it can be regarded as a clinical parameter or indicator of a more severe illness during hospitalization [54]. Implementing

Conclusion
COVID-19 has had a rapid spread globally. It has been a worldwide pandemic partly due to some similarities to other viral diseases such as influenza, MERS, SARS, and EVD; therefore, many people were not aware of its substantial risk in the early stages of this newly emerging disease. It has a longer median incubation, a longer period of infectivity, higher case-fatality rates with comorbidities, and higher asymptomatic viral loads. Fever happens in only can be future research topics.