COVID-19 pandemic has affected almost every part of the globe with more than 14 million cases of infection and 0.6 million death until second week of July 2020. According to WHO, the infection has spread to 216 countries including United States of America, Brazil, India and Russia being the most affected ones. The infection is caused by a novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) that causes Coronavirus Disease 2019 (COVID-19). This pandemic originated as an outbreak in Wuhan, Hubei province in China at the end of 2019. Small animals like pangolin or bat are speculated to be the initial source of human infection in China leading to a local outbreak in Wuhan. Later, the infection spread its tentacles across the world through travellers and it was declared a pandemic by WHO on 11th March 2020. The longer incubation period, aerosol-mediated and air-borne spread resulted in high transmission rate, thereby infecting the humans at an unprecedented scale. The pandemic was fuelled further by the undiagnosed asymptomatic cases. Therefore, WHO recommended “isolation” of the infected patients and quarantining” of the individuals who encountered the patients. Most of the countries implemented “lockdown” to take care of the ever-increasing cases and recommended “social distancing” to minimize human interactions. The pandemic has devastated all walks of life but the only saving grace is healing of the nature and nurturing of the environment. Thus, we have less polluted environment, more pristine forests and cleaner water bodies. The pandemic has impacted the social life and global economy as well.
SARS CoV2 is a Betacoronavirus that is similar to the other two human viruses including SARS and Middle East respiratory syndrome (MERS) of the same group. SARS-CoV-2 is spherical in shape having crown like surface structure formed by the spike (S) protein. Its genome is negative sense single stranded RNA of 30Kb that codes for 4 structural and 16 non-structural proteins. The S, M (membrane), E (envelope) and N (nucleocapsid) are the proteins present on the surface of the virion. The non-structural proteins play a pivotal role in viral replication within the host cell cytoplasm following the entry of the virus.
The COVID-19 patients show diverse clinical manifestations and results in asymptomatic, mild, severe and critical illness. The intense host immune response due to infection of the lower respiratory tract leads to the generation of “cytokine storm”. Further, complications like respiratory and multi-organ failure and septic shock in many cases cause death. Certain individuals (elderly, males, and type A blood group) and people with co-morbidities (diabetes, hypertension, existing respiratory disease, etc) are vulnerable to the infection. The diagnosis is primarily based on the real time PCR assays during first few days of infection. At a later stage, the infection is detected by serological methods including rapid tests or ELISA that are based on the identification of IgM/IgG. The treatment of the patients is symptomatic in the absence of antiviral drug and prophylactic vaccine. Antipyretics, antiviral and supplements are used for the treatment. However, clinical trials of several antivirals and drugs are going on at war footing to contain this infection. Interestingly, several vaccine candidates are also under clinical trials across the globe.
The present book deals with all the significant aspects of the ongoing COVID-19 pandemic including pathogen (morphology, genome, proteins, structural protein genes, replication), global epidemiology, transmission, risk factors, clinical manifestation, management, host immune response, pathogenesis, diagnosis, therapeutics (antiviral and other drugs, natural compounds) and vaccines.
We hope that this book will provide basic but relevant information about the different aspects of COVID-19 to the scientists, academicians and common citizens alike. Eventually, if this book inspires any one in any manner to become more civic and responsible citizen of the globe, we will achieve our goal.
Centre for Interdisciplinary Research in Basic Sciences
Jamia Millia Islamia, New Delhi,