Coronavirus
Coronavirus are zootonic viruses that are enveloped and have positive-sense, single-stranded RNA. Alpha, beta, gamma, and delta are the four genera of coronaviruses. The most pathogenic forms that have been found in their natural habitats, bats, are the alpha and beta forms. Besides, palm civets and camels are believed to have acted as the intermediate for transmitting SARS to humans. Out of the seven coronaviruses, the highly pathogenic and contagious Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) emerged in 2002. Middle East Respiratory Syndrome coronavirus (MERS-CoV) in 2012, and novel coronavirus or SARS-CoV-2 in 2019. But neither SARS-CoV nor MERS-CoV caused vast irreparable loss to humankind, as did SARS-CoV-2. These belong to beta genera along with SARS-CoV, hCoV-HKU1, and hCoV-OC43, while hCoV-NL63 and hCoV-229E belong to alpha genera.
The corona viruses genome ranges from 27000 to 32000 nucleotide bases in length. SARS causes severe clinical manifestations of the lower respiratory tract in humans by entering the mouth, nose, and eyes, leading to severe lung injury by targeting the epithelial cells and spreading the virus in different organs. The symptoms of SARS-CoV and MERS-CoV include fever, dry cough, and breath shortness. Some people also had diarrhea and nausea or vomiting. Other symptoms include loss of taste and smell, rash in skin, aches and pains in body, sore throat, conjunctivitis, diarrhea, headache, or fingers or toes discoloration. However, breathing difficulty or breath shortness, chest pain or pressure, and speech or movement loss are the severe symptoms of COVID-19. SARS-CoV-2 spreads via close contact with humans who inhale aerosols or droplets from infected individuals coughing, sneezing, talking, or singing. Reverse transcription-polymerase chain reaction (RT-PCR) using nasal and throat swabs are the gold standard for testing the infection. In contrast, antibody and antigen-based tests can be performed using blood samples. [AHM Nurun Nabi]
