Coronaviruses are a large family of viruses. Some cause illness in people, and others, such as canine and feline coronaviruses only infect animals. Coronaviruses include enveloped viruses and cause the common cold. There are four endemic strains that circulate commonly in humans, including human coronavirus 229E, OC43, NL63 and HKU1. These endemic strains generally cause mild flu-like symptoms, but can also cause more serious pneumonia in vulnerable populations.

When new coronaviruses ump from zoonotic hosts (bats, birds, camels, etc) to humans, they can result in a much more severe respiratory disease that can spread quickly through the population. Examples of such outbreaks include (SARS) (Severe Acute Respiratory Syndrome in 2003, caused by sARS-associated coronavirus (SARS-CoV), which resulted in an outbreak that infected over 8,000 people worldwide and was 10% fatal and MERS (Middel Eastern Respiratory Syndrom) in 2012, caused by MERS-CoV, which has infected over 2,500 people with about 35% fatalities. A new coronavirus, named SARS-CoV-2, became a serious global outbreak causing a severe respiratory disease referred to as COVID-19 and became a global pandemic. (US Patent No: 11,370,828).

Coronaviruses (CoVs) have a global distribution and infect a variety of human and animal hosts,. The International Commitee for Taxonomy of Viruses reprots four coronavirus genera; Alphacoronaviruses, Betacoronavirues, Gammacoronaviruses and Deltacoronaviruses.

Structure:

Coronaviruses (CoVs) are enveloped  single-stranded, positive-sense RNA viruses with genomes ranging between 26.2-31.7 kb, the largest amount known RNA viruses.

Structural Proteins Important for Infectivity

Four structural proteins are important for coronavirus infectivity;

E protein: is present in sub-stoichiometric amouns and acts as an enhance of budding.

M Protein: the integral membrane proteine M adapts a region of membrane for virus assembly and captures other structural proteins at the budding site.

M proteins from MHV, FCoV, SARS-CoV and transmissible gastroenteritis virus (TGEV) and Bovine coronavirus are targeted to the vicinity ofthe Golgi apparatus. Everse genetic studies and VLP assembly studies suggest that M protein promotes assembly by interacting with viral ribonucleoptortein (RNA) and S glycoproteins at the budding site, and by forming a network of M-M interacitons that is capable of excluding some host membrane proteins form the viral envelope. (J Struct Biol. 2011, Apr 174(a); 11-22).

N (nucleocapsid) protein: chaperones and protects the viral RNA genome.

Proteins associated with nucleic acid are known as nucleoproteins, adn the assocaition of viral capsid proteins with viral nucleic acid is called a “nuclocapsid”.

The N-protein is the most abudnant protein in coronavirus, highly immunogenicphosphoprotein and also normally very conserved. The N protein of coronavirus is often used as a marker in diagnostic assays.

The filamentous nucleocapsid is formed by the association of nucleocapsid (N) protein with single-stranded viral RNA.

S (Spikes): consisting of three copies of the S glycoprotein promote receptor binding and membrane fusion.

Types of Coronaviruses which infect Humans

SARS-CoV-2 Coronavius (COVID-19): see outline

SARS (severe acute respiratory syndrome) is a new coronavirus described in 2003.

Middle East Respiratory Syndrome Coronavius (MERC-coV): is a positive sense single stranded RNA virus first reported in 2012.

Types of coronaviruses which infect Animals

Mouse heptaits virus (MHV)

Feline coronavirus (FCoV)