COVID-19: A great threat to the human health

Ningombam Bishwamitra Singh *

INTRODUCTION :

The outbreak of the novel coronavirus is becoming a greatest challenge in the human society. The virus is known as the severe acute respiratory syndrome coronavirus 2(SARS-COV-2) and disease is the coronavirus disease 2019(covid-19).

The world health organisation (WHO) declared covid-19 a pendemic on March 11, 2020 which cause severe respirarory tract infections in human. This covid-19 outbreak was firstly reported at the end of the 2019 in Wuhan, Hubei, China.

SARS-COV-2 is a new member of the coronaviridae family which is distinct from SARS-COV (identity of approximately 79%) and MERS-COV (identity of approximately 50%). The sequence of the SARS-COV-2 shows similarity but distinct genome composition of SARS-COV and MER-COV.

The infection has spread to other regions in china and subsequently to other countries with increasing mortality rate. This covid-19 affected totally over 210 countries and territories. As of 28 April 2020, 11:00 GMT, the outbreak of COVID-19 reached 3,042,444 with recovered case 894,574 and death case 211,216.

PREVALENCE :

Fig.1 showing the total cases over the world

The spread of the covid-19 is increasing day by day globally . Total no. Of affected country and territory is 210.

As of April 28,2020, 11:00 GMT, the highest cases in USA is 1,010,507 total cases including death case of 56,803 which is followed by Spain having 232,138 cases including death case of 23,822.

Fig.2 showing the records of India.

As per the record on 28 April, 2020, 11:00 GMT, the total number cases is 29,435 including 6,869 recovered and 934. In India, Maharastra is the highest affecting state with covid-19 having 8,068 including 342 death case which is followed by Gujarat having 3,301 total cases including 151 death case.

Goa is the first state which is free from covid-19. The five states of the northeast India are free from covid-19: Manipur, Sikkim, Tripura, Arunachal pradesh, Nagaland.

CAUSES :

Infection with the SARS-CoV-2 causes COVID-19. The virus appears to spread easily among people, and more continues to be discovered over time about how it spreads. Data has shown that it spreads from person to person among those in close contact (within about 6 feet, or 2 meters).

The virus spreads by respiratory droplets released when someone with the virus coughs, sneezes or talks. These droplets can be inhaled or land in the mouth or nose of a person nearby.It can also spread if a person touches a surface with the virus on it and then touches his or her mouth, nose or eyes.

SYMPTOMS :

Signs and symptoms of coronavirus disease 2019 (COVID-19) may appear two to 14 days after exposure. This time after exposure and before having symptoms is called the incubation period. Common signs and symptoms can include Fever, Cough, Shortness of breath or difficulty breathing, tiredness, sorethroat, loss of smell. Severe complications may include like Pneumonia, respiratory failure, heart problems, acute kidney failure, etc.

RISK FACTORS :

Risk factors for COVID-19 appear to include:
🞽 Recent travel from or residence in an area with ongoing community spread of COVID-19 as determined by CDC or WHO.
🞽 Close contact with someone who has COVID-19, , such as being within 6 feet, or 2 meters, or being coughed on — which can occur when a family member or health care worker takes care of an infected person

Immunopathology of COVID-19: The site of initial infection with SARS-CoV-2 is unknown and the pathogenesis of COVID-19 is still under investiga￾tion. For most patients, COVID-19 might affect only the lungs because it is mainly a respiratory disease.

Most patients also developed lymphopenia and pneumonia with characteristic pulmonary ground glass opacity changes on chest CT. In addition, the study of 41 hospitalized patients with high-levels of proinflam￾matory cytokines including IL-2, IL-7, IL-10, G-CSF, IP-10, MCP-1, MIP-1A, and TNFα were observed in the COVID-19 severe cases.

These findings are in line with SARS and MERS in that the presence of lymphopenia and "cytokine storm" may have a major role in the pathogenesis of COVID-19.This so-called "cytokine storm" can initiate viral sepsis and inflam￾matory-induced lung injury which lead to other complications including pneumonitis, acute respiratory distress syndrome (ARDS), respiratory failure, shock, organ failure and poten￾tially death. Further autopsy or biopsy studies are necessary to understand more details of this disease.

DIAGNOSIS:

Current diagnostic tests for coronavirus include reverse-transcription polymerase chain reaction (RT-PCR), real-time RT-PCR (rRT-PCR),and reverse transcription loop-mediated isothermal amplification (RT-LAMP) . RT-LAMP has similar sensitivity to rRT-PCR, is highly specific and is used to detect MERS-CoV .

According to current diagnostic criteria founded by the China National Health Commission, laboratory examinations, including nasopharyngeal and oropharyngeal swab tests, have become a standard assess￾ment for diagnosis of COVID-19 infection.

To identify patients earlier, two one-step quantitative RT-PCR (qRT-PCR) assays were developed to detect two different regions (ORF1b and N) of the SARS-CoV-2 genome . Three novel RT-PCR assays targeting the RNA-dependent RNA polymerase (RdRp)/helicase (Hel), spike(S), and nucleocapsid (N) genes of SARS-CoV-2 were developed.Among the three novel assays, the COVID-19-RdRp/Hel assay had the lowest limit of detection in vitro; highly sensitive and specific assays may help to improve the laboratory diagnosis of COVID-19.

The SARS-CoV E gene assay was more sensitive than the RdRp gene assay combined with the one-step RT-PCR system .The E gene PCR was sufficient to diagnose a SARS-CoV-2 infection but RdRp protocol was recommended to confirm a positive result. The overall positive rate of RT-PCR detection of SARS-CoV-2 infection in 4880 cases from one hospital in Wuhan was 38% .

The positive rate of PCR for oropharyngeal swabs is not very high: only 53.3% of COVID-19-confirmed patients had positive oral swabs tests . In a series of 51 patients with confirmed COVID-19 infection, 71% patients were RT-PCR positive at the first time of testing of throat swab or sputum samples.The RT-PCR results usually become positive after several days(2-8 days).

The current laboratory test is time-consuming, and a shortage of commercial kits delays diagnosis. For patients suffering from fever, sore throat, fatigue, coughing or dyspnea that is coupled with recent exposure, COVID-19 infection should be diagnosed with typical chest computerized tomography (CT) characteristics despite negative RT-PCR results.

TREATMENT :

🞽 Anti-viral
Ganciclovir (0.25 g every 12 h intravenously), and lopinavir/ritonavir tablets (400/100 mg twice daily). Remdesivir is currently under trials at more than ten medical institutions in Wuhan and has been known to prevent MERS-CoV.

🞽 Anti-malarial
An old anti-malarial, chloroquine phosphate, hydroxychloroquine has been effective in inhibiting the exacerbation of pneumonia due to its anti-viral and anti-inflammatory activities.

🞽 Herbal treatments
There was widespread use of Traditional Chinese Medicine during the last SARS-COV outbreak and it is currently being used in China. The five most commonly used herbs were Astragali Radix (Huangqi), Glycyrrhizae Radix Et Rhizoma (Gancao), Saposhnikoviae Radix (Fangfeng), Atractylodis Macrocephalae Rhizoma (Baizhu), and Lonicerae Japonicae Flo.

🞽 Antibodies
The development of vaccines and therapeutic antibodies against COVID-19 has important implications. Considering the relatively high identity of the receptor-binding domain (RBD) in SARS-CoV-2 and SARS-CoV, the cross-reactivity of anti-SARS-CoV antibodies with the COVID-19 spike protein was assessed.Monoclonal antibodies can only recognize a single antigen epitope, which limits the use of MAb114 and REGN-EB3 in the treatment of COVID-19.

However, the development of COVID-19-specific antibodies requires a long time. It is not easy to apply monoclonal antibodies for new pathogens to clinical practice in a short time.

🞽 . Convalescent plasma transfusion Convalescent plasma was administered early after symptom on￾set in the treatment of SARS.In a laboratory test, the COVID-19 virus was isolated from the bronchoalveolar lavage fluid of a critically ill patient, and it could be neutralized by sera from several patients .

The National Health Commission of China appealed to convalescent patients to donate blood for the treatment of COVID-19 infection. Convalescent plasma should be collected within two weeks after recovery to ensure a high neutralization antibody titer.The difficulty in obtaining plasma during convalescence limits its clinical application. Well-designed clinical trials are needed to further evaluate the efficacy and safety of convalescent plasma ther￾apy in patients with COVID-19 infection.

🞽 VACCINE

The structure of SARS-CoV-2 S protein has been revealed,and this should enable the rapid development and evaluation of medical countermeasures to address the ongoing public health crisis. The majority of the vaccines being developed for coronaviruses target the spike glycoprotein or S protein . Vaccine development is a long process, and no vaccines are available at the time of a pandemic outbreak.

Three vaccines are in the human trial and 67 vaccines are in the preclinical stage. Recently on 23rd April,2020, ChAdOx1 nCOV-19 developed from the adenovirus is a recombinant viral vaccine that has been modified to express the surface spike protein of SARS-COV-2.

To make available a vaccine to the market from the laboratory, it involves totally six stages:Stage1is the exploratory phase of genetic sequecing. Stage 2 is the preclinical test in the animals.Stage3 involves three phases:
phase 1 is that giving vaccine to few persons,
phase 2 is that giving vaccine to more people with different characteristics like age, health, etc.
phase 3 is such that vaccines are given to thousands of people and efficiency and safety.
Stage 4 is stage of regulatory review and approval.
Stage 5 is the stage of manufacturing in large scale.
Stage 6 is the stage of checking of quality control.

PREVENTION :

Although there is no vaccine available to prevent COVID-19, you can take steps to reduce your risk of infection. WHO and CDC recommend following these precautions for avoiding COVID-19:
🞽 Avoid large events and mass gatherings.
🞽 Avoid close contact (within about 6 feet, or 2 meters) with anyone who is sick or has symptoms.
🞽 Stay home as much as possible and keep distance between yourself and others (within about 6 feet, or 2 meters) if COVID-19 is spreading in your community, especially if you have a higher risk of serious illness. Keep in mind some people may have COVID-19 and spread it to others, even if they don't have symptoms or don't know they have COVID-19.
🞽 Wash your hands often with soap and water for at least 20 seconds, or use an alcohol-based hand sanitizer that contains at least 60% alcohol.
🞽 Cover your face with a cloth face covering in public spaces, such as the grocery store, where it's difficult to avoid close contact with others, especially if you're in an area with ongoing community spread. Only use nonmedical cloth masks — surgical masks and N95 respirators should be reserved for health care providers.
🞽 Cover your mouth and nose with your elbow or a tissue when you cough or sneeze. Throw away the used tissue.
🞽 Avoid touching your eyes, nose and mouth.
🞽 Avoid sharing dishes, glasses, bedding and other household items if you're sick.
🞽 Clean and disinfect high-touch surfaces daily.
🞽 Stay home from work, school and public areas if you're sick, unless you're going to get medical care. Avoid taking public transportation if you're sick.

CONCLUSION :

During the pendemic,the doctors,nurses and medical staffs play important roles for the welfare of the human health.

To reduce the trasmission rate and confirmed case, the government has taken up many control measures like lockdown public transportation, public places, all religious ceremony and implementating the treatment strategy, awareness about heath care like wearing mask, hand sanitization, social distancing. NGO's,local clubs and police help them to break the chain of transmission.

However, the transmission of the disease has not yet been eliminated. There is presently no vaccine or specific anti viral drugs to treat the critically ill patients so the confirmed cases and death cases is increasing globally. Reasearch is going on for the invention of drugs and vaccines. Indeed,Covid-19 outbreak has become a major challenge to the researchers and medical teams.

Let's stand together to fight the covid-19.

Reference:

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2. Prompetchara, Eakachai, Chutitorn Ketloy, and Tanapat Palaga. "Immune responses in COVID-19 and potential vaccines: Lessons learned from SARS and MERS epidemic." Asian Pac J Allergy Immunol 38.1 (2020): 1-9.
3. Cunningham, Anne Catherine, Hui Poh Goh, and David Koh. "Treatment of COVID-19: old tricks for new challenges." (2020): 1-2.
4. WHO update notifications.