Coronaviruses are a group of infections known for containing strains that cause potentially deadly diseases in mammals and birds. In humans they’re typically spread via airborne droplets of fluid produced by infected individuals.
Some rare but notable strains, including Wuhan coronavirus (2019-nCoV), and those responsible for severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS), can cause death in humans.
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.
Replication of The Virus
Following the entry of this virus into the cell, the virus particle is uncoated and the RNA genome is deposited into the cytoplasm.
The coronavirus RNA genome has a 5′ methylated cap and a 3′ polyadenylated tail. This allows the RNA to attach to ribosomes for translation.
Coronaviruses also have a protein known as a replicase encoded in its genome which allows the RNA 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, the 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 RNA 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 separate the proteins in the chain. This is a form of genetic economy for the virus, allowing it to encode the greatest number of genes in a small number of nucleotides.
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 in ferrets 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.
What cause the outbreak?
Chinese health authorities were the first to post the full genome of the 2019-nCoV in GenBankexternal icon, the NIH genetic sequence database, and in the Global Initiative on Sharing All Influenza Data (GISAIDexternal icon) portal, an action which has facilitated detection of this virus. CDC is posting the full genome of the 2019-nCoV viruses detected in U.S. patients to GenBank as sequencing is completed.
2019-nCoV is a betacoronavirus, like MERS and SARs, all of which have their origins in bats. The sequences from U.S. patients are similar to the one that China initially posted, suggesting a likely single, recent emergence of this virus from an animal reservoir.
Early on, many of the patients in the outbreak of respiratory illness caused by 2019-nCoV in Wuhan, China had some link to a large seafood and live animal market, suggesting animal-to-person spread. Later, a growing number of patients reportedly did not have exposure to animal markets, indicating person-to-person spread. Chinese officials report that sustained person-to-person spread in the community is occurring in China. Person-to-person spread has been reported outside China, including in the United States and other countries. Learn what is known about the spread of newly emerged coronaviruses.
Myth Busters about Corona virus
Basic protective measures against the new coronavirus
Wash your hands frequently
Wash your hands frequently with an alcohol-based hand rub or soap and water.
Why? Washing your hands with an alcohol-based hand rub or soap and water kills the virus if it is on your hands.
Practice respiratory hygiene
When coughing and sneezing, cover mouth and nose with flexed elbow or tissue – discard tissue immediately into a closed bin and clean your hands with alcohol-based hand rub or soap and water.
Why? Covering your mouth and nose when coughing and sneezing prevent the spread of germs and viruses. If you sneeze or cough into your hands, you may contaminate objects or people that you touch.
Maintain social distancing
Maintain at least 1 metre (3 feet) distance between yourself and other people, particularly those who are coughing, sneezing and have a fever.
Why? When someone who is infected with a respiratory disease, like 2019-nCoV, coughs or sneezes they project small droplets containing the virus. If you are too close, you can breathe in the virus.
Avoid touching eyes, nose and mouth
Why? Hands touch many surfaces which can be contaminated with the virus. If you touch your eyes, nose or mouth with your contaminated hands, you can transfer the virus from the surface to yourself.
If you have fever, cough and difficulty breathing, seek medical care early
Tell your health care provider if you have traveled in an area in China where 2019-nCoV has been reported, or if you have been in close contact with someone with who has traveled from China and has respiratory symptoms.
Why? Whenever you have fever, cough and difficulty breathing it’s important to seek medical attention promptly as this may be due to a respiratory infection or other serious condition. Respiratory symptoms with fever can have a range of causes, and depending on your personal travel history and circumstances, 2019-nCoV could be one of them.
If you have mild respiratory symptoms and no travel history to or within China
If you have mild respiratory symptoms and no travel history to or within China, carefully practice basic respiratory and hand hygiene and stay home until you are recovered, if possible.
As a general precaution, practice general hygiene measures when visiting live animal markets, wet markets or animal product markets
Ensure regular hand washing with soap and potable water after touching animals and animal products; avoid touching eyes, nose or mouth with hands; and avoid contact with sick animals or spoiled animal products. Strictly avoid any contact with other animals in the market (e.g., stray cats and dogs, rodents, birds, bats). Avoid contact with potentially contaminated animal waste or fluids on the soil or structures of shops and market facilities.
Avoid consumption of raw or undercooked animal products
Handle raw meat, milk or animal organs with care, to avoid cross-contamination with uncooked foods, as per good food safety practices.