A coronavirus is one of a number of viruses that cause diseases in mammals and birds. In humans, the viruses cause respiratory infections, including the common cold, which are typically mild, though rarer forms such as SARS, MERS and 2019-nCoV can be lethal. Symptoms vary in other species: in chickens, they cause an upper respiratory disease, while in cows and pigs coronaviruses cause diarrhea. There are no vaccines or antiviral drugs to prevent or treat human coronavirus infections.
Coronaviruses are in the subfamily Orthocoronavirinae in the family Coronaviridae, in the order Nidovirales. They are enveloped viruses with a positive-sense single-stranded RNA genome and a nucleocapsid of helical symmetry. The genome size of coronaviruses ranges from approximately 26 to 32 kilobases, the largest for an RNA virus.
The name “coronavirus” is derived from the Latin corona, meaning crown or halo, which refers to the characteristic appearance of the virus particles (virions): they have a fringe reminiscent of a crown or of a solar corona.
Coronaviruses were discovered in the 1960s. The earliest ones discovered were infectious bronchitis virus in chickens and two viruses from the nasal cavities of human patients with the common cold that were subsequently named human coronavirus 229E and human coronavirus OC43. Other members of this family have since been identified, including SARS-CoV in 2003, HCoV NL63 in 2004, HKU1 in 2005, MERS-CoV in 2012, and 2019-nCoV in 2019; most of these have been involved in serious respiratory tract infections.
After cell entry, the virus particle is uncoated and its genome enters the cell cytoplasm.
The coronavirus RNA genome has a 5′ methylated cap and a 3’polyadenylated tail,which allows the RNA to attach to ribosomes for translation.
Coronavirus genomes also encodes a protein called a replicase which allows the viral genome to be transcribed into new RNA copies using the host cell’s machinery. The replicase is the first protein to be made; once the gene encoding the replicase is translated, translation is stopped by a stop codon. This is known as a nested transcript. When the mRNA transcript only encodes one gene, it is monocistronic. A coronavirus non-structural protein provides extra fidelity to replication because it confers a proofreading function, which is lacking in RNA-dependent RNA polymerase enzymes alone.
The genome is replicated and a long polyprotein is formed, where all of the proteins are attached. Coronaviruses have a non-structural protein – a protease – which is able to cleave the polyprotein. This process is a form of genetic economy, allowing the virus to encode the greatest number of genes in a small number of nucleotides.
Human to human transmission of coronaviruses is primarily thought to occur among close contacts via respiratory droplets generated by sneezing and coughing.
Coronaviruses are believed to cause a significant proportion of all common colds in adults and children. Coronaviruses cause colds with major symptoms, such as fever and sore throat from swollen adenoids, primarily in the winter and early spring seasons. Coronaviruses can cause pneumonia – either direct viral pneumonia or a secondary bacterial pneumonia – and may cause bronchitis – either direct viral bronchitis or a secondary bacterial bronchitis. The much publicized human coronavirus discovered in 2003, SARS-CoV, which causes severe acute respiratory syndrome (SARS), has a unique pathogenesis because it causes both upper and lower respiratory tract infections. There are no vaccines or antiviral drugs to prevent or treat human coronavirus infections.
Seven strains of human coronaviruses are known:
*Human coronavirus 229E (HCoV-229E)
*Human coronavirus OC43 (HCoV-OC43)
*Severe acute respiratory syndrome-related coronavirus (SARS-CoV)
*Human coronavirus NL63 (HCoV-NL63, New Haven coronavirus)
*Human coronavirus HKU1
*Middle East respiratory syndrome-related coronavirus (MERS-CoV), previously known as novel coronavirus 2012 and HCoV-EMC.
*Novel coronavirus (2019-nCoV), also known as Wuhan coronavirus. (‘Novel’ in this case means newly discovered, or newly originated, and is a placeholder name.)
*The coronaviruses HCoV-229E, -NL63, -OC43, and -HKU1 continually circulate in the human population and cause respiratory infections in adults and children world-wide
CLICK & SEE …>Phylogenetic tree of coronaviruses
The 2019 novel coronavirus, informally known as the Wuhan coronavirus, is a contagious virus that causes 2019-nCoV acute respiratory disease, a respiratory infection. It is the cause of the ongoing 2019–20 Wuhan coronavirus outbreak, a global health emergency. Genomic sequencing has shown that it is a positive-sense, single-stranded RNA coronavirus…….CLICK & SEE
As of 10 February 2020, there have been 1,015 confirmed deaths and more than 42,850 confirmed cases in the coronavirus pneumonia outbreak. The Wuhan strain has been identified as a new strain of Betacoronavirus from group 2B with an ~70% genetic similarity to the SARS-CoV. The virus was suspected to have originated in snakes, but many leading researchers disagree with this conclusion. The virus has a 96% similarity to a bat coronavirus, so an origin in bats is widely.
Common Symptoms of Coronavirus:
The symptoms of most coronaviruses are similar to any other upper respiratory infection, including runny nose, coughing, sore throat, and sometimes a fever. In most cases, you won’t know whether you have a coronavirus or a different cold-causing virus, such as rhinovirus.
Coronaviruses primarily infect the upper respiratory and gastrointestinal tract of mammals and birds. They also cause a range of diseases in farm animals and domesticated pets, some of which can be serious and are a threat to the farming industry. In chickens, the infectious bronchitis virus (IBV), a coronavirus, targets not only the respiratory tract but also the urogenital tract. The virus can spread to different organs throughout the chicken. Economically significant coronaviruses of farm animals include porcine coronavirus (transmissible gastroenteritis coronavirus, TGE) and bovine coronavirus, which both result in diarrhea in young animals. Feline coronavirus: two forms, feline enteric coronavirus is a pathogen of minor clinical significance, but spontaneous mutation of this virus can result in feline infectious peritonitis (FIP), a disease associated with high mortality. Similarly, there are two types of coronavirus that infect ferrets: ferret enteric coronavirus causes a gastrointestinal syndrome known as epizootic catarrhal enteritis (ECE), and a more lethal systemic version of the virus (like FIP in cats) known as ferret systemic coronavirus (FSC). There are two types of canine coronavirus (CCoV), one that causes mild gastrointestinal disease and one that has been found to cause respiratory disease. Mouse hepatitis virus (MHV) is a coronavirus that causes an epidemic murine illness with high mortality, especially among colonies of laboratory mice. Sialodacryoadenitis virus (SDAV) is highly infectious coronavirus of laboratory rats, which can be transmitted between individuals by direct contact and indirectly by aerosol. Acute infections have high morbidity and tropism for the salivary, lachrymal and harderian glands.
A HKU2-related bat coronavirus called swine acute diarrhea syndrome coronavirus (SADS-CoV) causes diarrhea in pigs.
Prior to the discovery of SARS-CoV, MHV had been the best-studied coronavirus both in vivo and in vitro as well as at the molecular level. Some strains of MHV cause a progressive demyelinating encephalitis in mice which has been used as a murine model for multiple sclerosis. Significant research efforts have been focused on elucidating the viral pathogenesis of these animal coronaviruses, especially by virologists interested in veterinary and zoonotic diseases
In domestic animals:
*Infectious bronchitis virus (IBV) causes avian infectious bronchitis.
*Porcine coronavirus (transmissible gastroenteritis coronavirus of pigs, TGEV).
*Bovine coronavirus (BCV), responsible for severe profuse enteritis in of young calves.
*Feline coronavirus (FCoV) causes mild enteritis in cats as well as severe Feline infectious peritonitis (other variants of the same virus).
the two types of canine coronavirus (CCoV) (one causing enteritis, the other found in respiratory diseases).
*Turkey coronavirus (TCV) causes enteritis in turkeys.
*Ferret enteric coronavirus causes epizootic catarrhal enteritis in ferrets.
*Ferret systemic coronavirus causes FIP-like systemic syndrome in ferrets.
*Pantropic canine coronavirus.
*Rabbit enteric coronavirus causes acute gastrointestinal disease and diarrhea in young European rabbits. Mortality rates are high.
*A new veterinary disease, porcine epidemic diarrhea virus (PED or PEDV), has emerged around the world. Its economic importance is unclear but shows high mortality in piglets.
There is no medicine for the virus but only symtomatic treatment is given to reduce the symtems.
The following protective measures may be taken to protect oneself. :
What to Do About Coronavirus
There is no vaccine for coronavirus. To help prevent a coronavirus infection, do the same things you do to avoid the common cold:
Wash your hands thoroughly with soap and warm water or with an alcohol-based hand sanitizer.
Keep your hands and fingers away from your eyes, nose, and mouth.
Avoid close contact with people who are infected.
You treat a coronavirus infection the same way you treat a cold:
Get plenty of rest.
Take over-the-counter medicine for a sore throat and fever. But don’t give aspirin to children or teens younger than 19; use ibuprofen or acetaminophen instead.
A humidifier or steamy shower can also help ease a sore and scratchy throat.
Even when a coronavirus causes MERS or SARS in other countries, the kind of coronavirus infection common in the U.S. isn’t a serious threat for an otherwise healthy adult. If you get sick, treat your symptoms and contact a doctor if they get worse or don’t go away.