Alphacoronaviruses (Alpha-CoV) are members of the first of the four genera (''Alpha''-, ''
Beta-'', ''
Gamma-'', and ''
Delta-'') of
coronavirus
Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the co ...
es. They are
positive-sense, single-stranded
RNA virus
An RNA virus is a virusother than a retrovirusthat has ribonucleic acid ( RNA) as its genetic material. The nucleic acid is usually single-stranded RNA (ssRNA) but it may be double-stranded (dsRNA). Notable human diseases caused by RNA virus ...
es that infect
mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s, including
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
s. They have spherical virions with club-shaped
surface projections formed by trimers of the
spike protein, and a
viral envelope
A viral envelope is the outermost layer of many types of viruses. It protects the genetic material in their life cycle when traveling between host cells. Not all viruses have envelopes.
Numerous human pathogenic viruses in circulation are encase ...
.
Alphacoronaviruses are in the subfamily ''
Orthocoronavirinae
Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the c ...
'' of the family ''
Coronaviridae''. Both the ''Alpha''- and ''Betacoronavirus'' lineages descend from the
bat viral gene pool. Alphacoronaviruses were previously known as "