Coronaviridae [Coronavirus]: The Coronavirus or COVID-19 has been put together in one genus which also constitutes the family Coronaviridae. The coronaviruses better know after the name of the species in which they produce infection. Coronaviridae is a family of enveloped, positive-sense, single-stranded RNA viruses. Thus, coronaviruses causing respiratory infection in humans know as human coronavirus. These are being described hereunder in brief.
The virus is spherical with a diameter in the range of 80- 200 nm. Pleomorphism exhibit by the virion because of the flexibility of the envelope. The surface covers with projections that have a size of 10-20 nm. These surface projections give the appearance of a halo around the virus which gives it the name corona. A single-stranded RNA comprises the genome of the virus.
Genome replication occurs entirely in the cytoplasm and begins with the binding of the virion to specific glycoprotein receptors of the host cell membrane. The virus is then able to penetrate the cell surface by S protein-mediated fusion of the viral envelope with plasma or endosomal membranes. After uncoating occurs, the genomic RNA serves as the mRNAs for translation and polyprotein processing. This follows by RNA replication to synthesize genomic RNA and subgenomic mRNAs. Virus particles assemble and release by exocytosis.
3] Polypeptide and Antigens:
Most coronaviruses comprise three to five structural proteins in addition to a nucleoprotein which associates with the genomic RNA. Two species of glycoproteins are located in the envelope. All the structural proteins of coronaviruses are antigenic.
4] Clinical Features:
The clinical picture produced by coronaviruses resembles that of rhinoviruses with the difference that whereas the incubation period in rhinovirus infection is shorter, the duration of illness is longer in coronavirus infection. The proportion of common cold that can be associated with coronaviruses is in the range of 2-10%. The role of coronaviruses in causing lower respiratory tract infections not yet defines.
5] Laboratory Diagnosis:
The laboratory diagnosis can be based on isolation and identification of coronavirus as well as detection of antigen or antibody by serological techniques. The best isolation of coronaviruses has been seen in organ cultures derived from the human embryonic trachea (HETOC). Though various cell lines have also been defined, none can recommend for the isolation of all coronaviruses. Antibodies to these viruses can detect in the serum by virus neutralization, complement fixation test, indirect haemagglutination, immune adherence, haemagglutination, radial hemolysis, and ELISA. The viral antigen can detect with immunofluorescence and ELISA techniques.
6] Prophylaxis and Treatment:
No successful vaccination has resulted against coronaviruses because of the antigenic variation in the serotypes of coronaviruses and the failure of antibodies to protect against the infection. The use of antiviral chemotherapy has also been unproductive so far.
During 2003 the world was hit by a fast-spreading virus that was transmitted through droplets and attacked those who came in close contact with the patients of this new clinical syndrome called a severe acute respiratory syndrome (SARS). The clinical picture was exemplified by atypical pneumonia and fever for which no other cause could be demonstrated. A coronavirus that had not hitherto affected the human population was isolated from these patients and designated as SARS-CoV. The virus could detect by PCR using specific primers. Antibody detection test kits based upon ELISA and IFAT techniques have also developed. The use of standard precautions while handling the patients or their biological material drastically cuts short the transmission of this infection.
Affect by Coronaviridae [Coronavirus]:
How can affect to Humans? Coronaviridae is a family of single-stranded, positive RNA viruses. Members of this family include Coronaviruses and Toroviruses. Both are capable of causing mild respiratory and enteric infections in humans and other vertebrate animals. Coronaviruses also know to cause severe infections such as SARS (severe acute respiratory syndrome). In humans, the viruses cause respiratory infections, including the common cold, which are typically mild, though rarer forms such as SARS, MERS, and COVID-19 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. Also, they have 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.
Treatment for Coronaviridae [Coronavirus]:
The standard of care for the treatment SARS-CoV infection during the 2003 epidemic was the use of the antiviral ribavirin in combination with high doses of steroids but there is no supportive evidence of the effectiveness of this therapy. The latest research (In 2020) for the treatment of Coronavirus or COVID-19, Nothing. Only, keep distancing up to 4 meters, maintain social distance, and wash hands from time to time.
Prevention of Coronaviridae [Coronavirus]:
The best preventive measures for the spread of human SARS is through the use of public health measures and good infection control practices. Currently, there are no vaccines available for preventing human SARS, but there are effective vaccines for common veterinary coronaviruses. The latest research (In 2020) for the prevention of Coronavirus or COVID-19 by China, Coronavirus can float in the air [Air pollution] to 4 meters. So, keep distancing up to 4 meters, and keep wash hands from time to time.
- Essentials of Medical Microbiology, Book by RL Ichhpujani and Rajesh Bhatia.