Emerging Human Coronavirus Infections (SARS, MERS, and COVID-19): Where They Are Leading Us

Abstract

Coronavirus infections are responsible for mild, moderate, and severe infections in birds and mammals. These were first isolated in humans as causal microorganisms responsible for common cold. The 2002-2003 SARS epidemic caused by SARS-CoV and 2012 MERS epidemic (64 countries affected) caused by MERS-CoV showed their acute and fatal side. These two CoV infections killed thousands of patients infected worldwide. However, WHO has still reported the MERS case in December 2019 in middle-eastern country (Saudi Arabia), indicating the MERS epidemic has not ended completely yet. Although we have not yet understood completely these two CoV epidemics, a third most dangerous and severe CoV infection has been originated in the Wuhan city, Hubei district of China in December 2019. This CoV infection called COVID-19 or SARS-CoV2 infection has now spread to 210 countries and territories around the world. COVID-19 has now been declared a pandemic by the World Health Organization (WHO). It has infected more than 16.69 million people with more than 663,540 deaths across the world. Thus the current manuscript aims to describe all three (SARS, MERS, and COVID-19) in terms of their causal organisms (SARS-CoV, MERS-CoV, and SARS-CoV2), similarities and differences in their clinical symptoms, outcomes, immunology, and immunopathogenesis, and possible future therapeutic approaches.

How could we forget immunometabolism in SARS-CoV2 infection or COVID-19?

“…The details of the immune response associated with COVID-19 immunopathogenesis have been described in detail by the author in his recent publication [9,16]. Hence, interested readers should also read these articles for details.…”

“…Hence, SARS-CoV2 exploits ACE2 expression via IFNs to increase the infection severity. The details of SARS-CoV causing SARS, MERS-CoV causing middle eastern respiratory syndrome (MERS), and most recent SARS-CoV2 responsible for COVID-19 are described by the author in detail somewhere else [9,16].…”

Understanding the complexities of SARS-CoV2 infection and its immunology: A road to immune-based therapeutics

“…Severe COVID-19 patients also show neurological symptoms (headache, loss of taste and smell, and vision impairment etc. ), described in detail somewhere else [19] , [55] , [56] . Ageusia (loss of taste) occurs specifically to the COVID-19 patients as compared to other flu-like upper respiratory infections [57] .…”

“…Pneumonia is one of the major symptoms of the COVID-19 causing acute lung injury (ALI) or acute respiratory distress syndrome (ARDS) to put the patient on the respiratory support system (ventilator). Chest radiographs of some patients show ground-glass lung changes, normal or lower than average WBC count, and platelet counts, hypoxemia, along with kidney and liver dysfunction [19] . The gastrointestinal symptoms (vomiting, diarrhea, nausea, and abdominal discomfort) occur in some COVID-19 patients first, before fever and cough indicating its feco-oral transmission [63] .…”

“…Bats serve as crucial animal reservoirs for EIDs (Marburg virus infection, Nipah virus infection, Rabies virus infection, Ebola virus infections, severe acute respiratory syndrome or SARS, and Middle Eastern respiratory syndrome or MERS) in humans [17] , [18] . SARS originated from Guangdong district in China in year 2002–2003 (spread to thirty countries worldwide) due to SARS-CoV and MERS first reported in a hospital in Jeddah, Saudi Arabia with the death of the patient in 2012 due to MERS-CoV that spread to twenty seven countries worldwide causing an epidemic are [19] , [20] . Both, these viruses belong to the Coronaviridae family and are betacoronaviruses (βCoVs).…”