Coronaviruses belong to the Coronavirinae subfamily, which is divided into four genera based on their phylogenetic relationships and genomic structures: Alphacoronavirus, Betacoronavirus, Gammacoronavirus, and Deltacoronavirus. Only mammals can be infected by alphacoronaviruses and betacoronaviruses. Distance learning has its strengths and limitations. A few are enumerated. Gammacoronaviruses and deltacoronaviruses can infect mammals in some cases. Human respiratory diseases are commonly caused by alphacoronaviruses and betacoronaviruses. The two viruses, SARS-CoV and MERS-CoV are highly pathogenic forms and can lead to severe respiratory syndrome in humans, but other human coronaviruses strains like (HCoV-NL63, HCoV-229E, HCoV-OC43 and HKU1) can also cause mild upper respiratory diseases. The origin of SARS-Cov-2 is unknown at this time, but genomic studies indicate that it evolved from a strain found in bats (BatCov RaTG13). Human-to-human transmission, like that of other respiratory pathogens, is primarily via aerosol. Clinical reports suggest that the most frequent symptoms of COVID-19 are fatigue, fever, dry cough, sore throat, dyspnoea, and diarrhea.
Milagros D. Samaniego-Picota