A short review on COVID-19: A great concern to public health

Received: June 07, 2020; Accepted: June 22, 2020; Published: June 25, 2020 Abbreviations: CoV: Coronavirus; DMV: Double membrane vesicles; FDA: Food and drug administration; hAPN: Human aminopeptidase N; ORF: Open reading frame; SARS: Severe acute respiratory syndrome; IFN: Interferon; MERS: Middle east respiratory syndrome; NHP: Non-human primate; TMPRSSII: Transmembrane protease; HCoV: Human coronavirus; PEDV: Porcine epidemic diarrhea virus; RBD: Receptor binding domain; hACE2: Human angiotensin converting enzyme 2.


Introduction
The first severe acute respiratory syndrome coronavirus (SARS-CoV) outbreak in China (in 2003), which spreads out in 29 countries so far and infected about 9000 people with more than 10% mortality [1]. Soon after five more human coronaviruses (HCoV-229E, HCoV-HKU1, HCoV-NL63, and HCoV-OC43) are found also to be associated with a range of respiratory symptoms, including high-morbidity outcomes such as pneumonia and bronchiolitis [2]. In 2012, another virus MERS-CoV (Middle East Respiratory Syndrome coronavirus), was isolated from a patient with pneumonia in Saudi-Arabia [3]. However, a very recent outbreak of a more severe acute respiratory syndrome (SARS)associated coronavirus (SARS-CoV-2) which one causes COVID-19 disease, a most concerned factor, now-a-days, to human health. Not only the health but it caused a disaster in human social, economic and many other aspects of life, being the disease is highly infectious and fatal too. (Several Review by CDC, WHO, NIH, etc).
In fact, Sars-CoV-2 is originated on 26 th December 2019 at Wuhan city of China, and causes a life-threatening pneumonia, and is the most pathogenic human coronavirus identified so far [4]. No statistical data at this point would be perfect since the disease progression as well as mortality rate is increasing at an exponential rate. As of April 4 th , 2020, according to CNN reports, the worldwide infected cases are about 1,192,028; Deaths 64,316. In USA, infected cases are 308,533 and death 8,376.
In this review, we summarize the current knowledge on human coronavirus COVID-19 (since now will be mentioned as such) infection emphasizing on its impact in human life.

Sources of corona virus and zoonosis
Sars-CoV-2 like other human corona virus, MERS-CoV, SARS-CoV, has is originated from Bats [5]. The zoonosis has shown in Table 1.
Like Flu virus, SARS-CoV-2 are capable to infect the respiratory system, and facilitating the spread through coughing and sneezing, especially to the immune-compromised and the elderly people [6], However, unlike to other common cold or allergy issues, SARS-CoV-2 attack mainly lower respiratory tract, and results deadly Pneumonia [7]. No medicine is there yet, either control and/or cure, but only several efforts for prevention.

Diagnosis of corona virus in human
Chest radiography can reveal a typical feature of bronchiolitis. Identification of unknown pathogens using molecular biology tools is difficult, but genome-specific PCR primers can be designed for RT-PCR analysis. The presence of restriction enzyme fragment length polymorphism (RFLP) can also be done.

COVID-19 (SARS-Cov-2) may be seasonal endemic pathogen
New Coronavirus COVID-19 that's marked by fevers, coughing, and occasionally severe lung infections, eventually may become a part of the human respiratory-virus repertoire and may not go away without a proper vaccine.

Approach for finding therapeutics
Coronaviruses are classified into four distinct phylogenetic groups, a-coronaviruses, b-coronaviruses and g-acoronaviruses which infect mammals, and d-coronaviruses infect avian species [9]. Among all known human coronaviruses (HCoV), SARS-CoV-2, like SARS-CoV and MERS-CoV belongs to a β-corona virus family cause Lower track respiratory problems, whereas others belong to α-type cause only mild upper track infection.
No specific treatment is currently available for human coronaviruses to date, but using the genome knowledge from six previously discovered human coronaviruses, the investigators are examining the progress of the use and development of therapeutic drugs, focusing on the potential roles of virus inhibitors [10]. The innate immune system has a major protective role as the first line of defense against respiratory pathogens. The Receptor determinant identified as N-acetyl-9-O-acetylneuraminic acid or O-Acetylated Sialic acid interferon (IFN) system orchestrates hundreds of different cellular effector proteins that protect the epithelial barrier by altering the physiological and cellular environment, and also impair virus propagation, spread and transmission.
In general, HCoVs do not elicit a strong innate immune response in primary target cells of the human airway early during infection. Despite the presence of all major pathogen recognition receptors, no elevated expression of IFN beta, pro-inflammatory cytokines or interferon stimulated genes can be observed up to 12 h post-infection in HAEs infected with HCoV-229E, MERS-or SARS-CoVs [11]. This is most likely due to the intrinsic CoV properties harbored in the replicative non-structural proteins that actively aid in avoiding recognition by the host innate immune system. For example, the 5′ termini of the viral mRNA are capped making them indistinguishable from the host cellular mRNAs and no longer detectable by cellular sensors.
Vaccines using the spike proteins of both SARS-and MERS-CoVs have proven protective in animal models [12], suggesting that a vaccine against HCoVs for human use might be achievable. Until any specific Trends in Res, 2020 doi: 10.15761/TR.1000167 remedies against COVID-19 becomes available, we must rely on preventive measure that we have displayed in the Table 2.

Conclusions
Studies with many HCoVs indicate that HCoVs including COVID-19 may be more clinically important in the immunecompromised and/or elderly people than previously thought. Since vaccines are not currently available for any of these respiratory viruses, it is necessary to monitor epidemic patterns and investigate the spread of respiratory infections to efficiently identify, control and prevent epidemics.
A detailed study of COVID-19, both genomics and proteomics is needed to know the infection mechanism as well as to drug design. This, however, may be hampered by the lack of an appropriate in vitro as well as in vivo model. Further, future experiments with more sensitive diagnostic tools should yield a more accurate picture of the prevalence of this virus (COVID-19) and its association with respiratory diseases.