__Coronaviruses__ are a group of related viruses that cause diseases in mammals and birds. In humans, coronaviruses cause respiratory tract infections that can be mild, such as some cases of the common cold (among other possible causes, predominantly rhinoviruses), and others that can be lethal, such as severe acute respiratory syndrome, Middle East respiratory syndrome, and coronavirus disease 2019 - wikipedia 
Coronavirus. Subfamily of viruses in the family Coronaviridae
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The name ''coronavirus'' is derived from the Latin ''corona'', meaning "crown" or "halo", which refers to the characteristic appearance reminiscent of a crown or a solar corona around the virions (virus particles) when viewed under two-dimensional transmission electron microscopy, due to the surface covering in club-shaped protein spikes.
Symptoms in other species vary: in chickens, they cause an upper respiratory tract infection, while in cows and pigs they cause diarrhea. There are yet to be vaccines or antiviral drugs to prevent or treat human coronavirus infections.
# Outbreaks of coronavirus-related diseases
Coronaviruses constitute the subfamily __''Orthocoronavirinae__'', in the family ''Coronaviridae'', order ''Nidovirales'', and realm ''Riboviria''. They are enveloped viruses with a Positive-sense single-stranded RNA virus RNA genome and a nucleocapsid of helical symmetry.
# Genetics
The genome size of coronaviruses ranges from approximately 27 to 34 kilobase, the largest among known RNA viruses.
# Sections