A review on the COVID-19, its history, diagnostic approaches, role of herbs and current world scenario

COVID- 19, a novel coronavirus disease caused by SARS-CoV-2 (severe acute respiratory syndrome caused by coronavirus-2) transmitted from person to person, is now declared as a pandemic worldwide by WHO. SARS-CoV-2 belongs to the family of Coronaviridae . Covid-19 (Coronavirus disease 2019) is an infectious disease with clinical symptoms like fever, sore throat, sneezing, shortness of breath, fatigue, cough, diarrhoea, chills, and respiratory symptoms that has now entered into the new dangerous phase. This virus can easily extend and can cause severe illness to the global village. Till 7 Nov 2020, the total number of confirmed COVID-19 cases was 48534508, and the death number is 1231017, affecting, directly and indirectly, more than 215 territories worldwide. Hence an effective international strategy is required to control and prevent this disaster. To combat the coronavirus-2 different approaches have been initiated in scientific concern, but focussed attention should be given to the medical value of herbal plant extract to prevent these endemic type diseases. Hence, this review describes the symptoms and the role of herbal plants in treating the COVID-19.


INTRODUCTION
rom December 2019, the novel coronavirus 2019 (COVID-19) disease, an unexpected pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome caused by coronavirus-2), has caused severe panic to the global village. The coronavirus causes illness (alveolar injury as well as progressive respiratory stoppage), which finally leads to the death of the suffering person (1).
Developed and developing countries are continuously maximizing their efforts to control the spread of the virus and minimize the infection. Despite its similarity with the SAR-CoV virus, its diagnostic approaches and transmission efficiency are different, which is probably due to the change in nucleotide spike protein and its RBD (receptor binding domain) structure (2). To overcome this situation, a drug or a vaccine is urgently required to prevent mortality and morbidity. Many drugs are undergoing the clinical trial phase. Herbal medicinal plants are found promising in treating various diseases and may play a crucial role in defeating and treating this pandemic virus (3,4).

COVID-19 Overview
Coronavirus is a fast-spreading virus capable of causing multiple system infection in animals, including BCoV (bovine respiratory Coronavirus) in cows, MHV (mouse hepatitis virus) in mouse, IBV (infectious bronchitis virus), also called as the avian virus in birds and chicken and severe respiratory infection such as MERS (Middle East respiratory syndrome) and SARS (severe acute respiratory syndrome) in humans (5,6). The COVID-19 causes chronic and acute enteric, central nervous, as well as respiratory system infections in humans. Coronavirus is named due to the presence of crown-like spikes on its surfaces; enveloped, positive-stranded RNA virus belongs to the genus of the Coronaviridae family, and its genomic RNA size is 27-32 kb (6,7). This novel Coronavirus belongs to the β Coronavirus, which is found to be close phylogenetically with bat SARS coronavirus exactly shares about 96.2% sequence similarity (8). Still, the exact origin of the COVID-19 virus remains a mystery to worldwide researchers, and researchers need to pinpoint the exact COVID-19 source (9). SARS-CoV-2 (severe acute respiratory syndrome caused by coronavirus-2) genomes have found mutated and can be divided into three types (Type A, Type B, and Type C). Type A and Type C major portions are found among Americans and Europeans. On the other side, Type B is mainly observed in East Asia (10). This virus in humans predominantly affects the upper respiratory tract with mild to severe illness (11).

History
In 1931, the first Coronavirus-based disease was diagnosed, while in 1965, from the humans first HCov-229E Coronavirus was isolated. However, SARS-CoV-1 (a member of sub-genus Sarbecovirus), which was realized as the often fatal respiratory infection, was firstly reported in 2002 in China with approximately 11% mortality (Fig. 1). The genome of SARS-CoV-1 is 29,727 nucleotides in length (12). Angiotensin-converting enzyme-2 (ACE-2) is a surface molecule present on the cells of the small intestinal epithelium and respiratory tract. This ACE-2 is a receptor for SARS-CoV-1 and plays a vital role in protection from lung failure (13 clinical symptoms of SARS-CoV-1 are fever, headache, cough, pneumonia, and dyspnea (11).
Later in 2012, in Saudi Arabia, MERS-CoV (Middle East respiratory syndrome coronavirus) causes endemic with a 34% mortality rate. It causes a viral respiratory infection (13). From infected camels, this virus is transmitted to humans (Fig. 1). Further, from 2012 to 2018, MERS-CoV cases were found in about 27 different countries, including Egypt and Qatar. The genome of MERS-CoV-1 is approximately 30,119 nucleotides in length, and DPP4 (dipeptidyl peptidase 4) is the receptor of MERS-CoV-1. DPP4 (multifunctional cell surface protein) protein is found on the epithelial cells of the kidney, respiratory tract, small intestine, liver and plays a crucial role in T cell activation (12). Some common symptoms of MERS-Ov-1 are sore throat, cough, abdominal pain, chest pain, fever, and vomiting (12).
This newly discovered Coronavirus (SARS-CoV-2) encodes a glycosylated spike protein, which is mainly responsible for binding with the receptor, ACE-2 (14). The genetic material (RNA) of SARS-CoV-2 is enclosed by a lipid-bilayer envelope (15). Some common mode of transmission includes fecal-oral route, contact with an infected person, and via respiratory droplets (4).

Symptoms of COVID-19
Coronavirus, a pandemic disease transmitted from one person to another via aerosol transmission, making it a threat for numerous individuals. Based on the collected information, the three common symptoms of COVID-19 are dry cough, fever, and difficulty in breathing, and other symptoms may include hypoxemia, a lesion in the lungs, tiredness, conjunctivitis, discoloration of toes or fingers, and diarrhea, as shown in figure 2 (4). These symptoms were approximate, observed within 5-6 days of infection (16).

Diagnostic method
In this pandemic situation, the test is the only way to control the spreading of COVID-19. The COVID-19 virus is normally spread via the respiratory route through droplets from the infected patients. According to the CDC (centers for diseases control and prevention), two types of the diagnostic test for COVID-19 is available. a) Antibody tests, which are also known as the serological test, are mainly used to determine whether the person already had a COVID-19 infection. In this test, a few drops of blood are taken from the individuals, and antibodies (IgM and IgG) can be detected by using conventional ELISA tests. This antibody test is a rapid test that gives results within 20 minutes. The drawback related to this test is its poor specificity and lower sensitivity (17,18).
b) Swab tests, Nasal (Nasopharyngeal) swab and throat (oropharyngeal) swab sample was collected from the patient and kept in viral medium (19). For higher sensitivity, both the nasal as well as throat swabs were combined together. Bronchoalveolar fluid, sputum, and faecal samples were also collected from the patients. The viral RNA is detected by using RT-PCR (reverse transcription-polymerase chain reaction). Many other antigen detection-based devices came into the market but had poor sensitivity (20).

COVID-19 Management
Some common FDA-approved drugs that are given to the hospital admitted COVID-19 patients include chloroquine, an antimalarial drug that inhibits the entry of Coronavirus. Studies have shown that the hydroxychloroquine, an analogue of chloroquine is more powerful and less toxic, can be used in place of chloroquine. In vitro condition, both the drug has effectively inhibited the SARS-CoV-2 activity (21). The clinical trial study performed in France and China provides evidence related to the effectiveness of both the drug (22). Other drug includes Ivermectin (antiparasitic drug), Camostat Mesylate (an anti-viral drug), Remdesivir (intravenous drug and found effective against MERS coronavirus), favipiravir (influenza drug), interferon-alpha (IFN-α), arbidol and ribavirin (23,24).
A research study confirm that glycyrrhizin, an active compound (derived from licorice roots), shows an anti-SARS-CoV effect by inhibiting the viral replication (26). Another active compound, glycyrrhizin, which is derived from the Glycyrrhiza glabra plant, also poses the anti-viral activity when tested in vitro against SARS-CoV, ten different clinical strains. The same results were also observed when baicalin, a compound derived from the Baikal skullcap plant, also displayed the anti-viral activity against SARS-CoV (27). It also inhibits the HIV-1 virus replication in vitro testing. Other herbal plants that pose the anti-viral activity against SARS coronavirus are the Eucalyptus tree, Japanese honeysuckle, and Korean ginseng, also known as Panax ginseng (27 (28). This Chinese herbal formulation is mainly used to treat infections like influenza, fever, cough, bronchitis, sneezing, muscle ache, and fatigue.
In the USA, clinical testing on the Lianhua-Qingwen drug is in the process (29). The Chinese government has already recommended the Lianhua-Qingwen drug for the prevention and treatment of COVID-19 (30).
The experimental results show that this herbal composition in a dose-dependent manner effectively inhibits the SARS-CoV-2 replication and also suppresses the pro-inflammatory cytokines release like IL-6 and TNF-α (28). And in the case of COVID-19 infections, an increase in cytokine was observed, so the obtained result will become more important.

Current world scenario
COVID-19 has adversely affected the health of humans throughout the world. At the time of preparing this manuscript on 7 Nov 2020, tabular data of the current world scenario was noted from the WHO dashboard (Table 2).

Preventive measures
Till date, there is no clinically proven treatment drug are available in the market for COVID suffering patients, so participation in the gathering should be avoided. According to WHO and ICMR guidelines, social distancing, avoiding the gathering, home isolation, and home quarantine if any symptoms were visualized (Fig. 3).

CONCLUSION
The recent outbreak of COVID-19 has now become a global threat to humanity. In this review, the information regarding the COVID-19, history, its symptoms, diagnostic method, management of COVID-19, and current world scenario has been summarized. As of now, no drug for the treatment of COVID-19 has been available for patients, and only a few numbers of allopathic drugs are found effective and are given to hospitalized patients. This review provides information and obvious evidence regarding the use of anti-viral herbal plant and their compounds as a preventive agent against SARS-CoV-2. These herbal plants in single or in combination can be served as an alternative preventive therapy against SARS-CoV-2. However, this hypothesis should be experimentally validated via SARS-Cov-2 infection models and clinically tested on COVID-19 patients.

ACKNOWLEDGEMENT
We would like to acknowledge TEQIP for the financial assistantship.