This article is about the group of viruses. For the disease involved in the 2019–20 coronavirus pandemic, see Coronavirus disease 2019. For the virus that causes this disease, see Severe acute respiratory syndrome coronavirus 2.<br />Orthocoronavirinae<br />Coronaviruses 004 lores.jpg<br />Transmission electron micrograph (TEM) of avian infectious bronchitis virus<br />SARS-CoV-2 without background.png<br />Illustration of the morphology of coronaviruses; the club-shaped viral spike peplomers, colored red, create the look of a corona surrounding the virion when observed with an electron microscope.<br />Virus classificatione<br />(unranked): Virus<br />Realm: Riboviria<br />Phylum: incertae sedis<br />Order: Nidovirales<br />Family: Coronaviridae<br />Subfamily: Orthocoronavirinae<br />Genera[1]<br />Alphacoronavirus<br />Betacoronavirus<br />Gammacoronavirus<br />Deltacoronavirus<br />Synonyms[2][3][4]<br />Coronavirinae<br />Coronaviruses are a group of related viruses that cause diseases in mammals and birds. In humans, coronaviruses cause respiratory tract infections that can range from mild to lethal. Mild illnesses include some cases of the common cold (which has other possible causes, predominantly rhinoviruses), while more lethal varieties can cause SARS, MERS, and COVID-19. Symptoms in other species vary: in chickens, they cause an upper respiratory tract disease, while in cows and pigs they cause diarrhea. There are yet to be vaccines or antiviral drugs to prevent or treat human coronavirus infections.