CORONAVIRIDAE FAMILY

Coronaviridae family is comprised of viruses known as coronaviruses. There are only two genera of viruses in the Coronaviridae family. Coronavirus (which contain Coronaviruses) and Torovirus (which contain Toroviruses) are the two main genera of Coronaviridae family. Both coronaviruses and toroviruses have a worldwide distribution. Viruses in this family include those that infect humans and other mammals such as pigs, mice, cattle, birds and bats. Coronaviruses are enveloped viruses that replicate in the cytoplasm of their host cell. Coronavirus are released from their host cell by a budding process via the cell membrane after completing the cycle of their replication in affected host cell. They have a ss(+)RNA genome and coronaviruses measure between 120-160 nm in diameter. Coronaviruses have a helical nucleocapsid. Viruses in this family cause respiratory infections in humans and other animals that they infect.

The commonest viral member of the Coronaviridae family is severe acute respiratory syndrome (SARS) coronavirus – that causes a severe respiratory infection or lung disease that is characterized by pneumonia of the lower respiratory tract of humans. In 2003, SARS coronavirus caused several outbreaks of SARS in most parts of the world; and the epidemic was marked by several morbidity and mortality especially in hospital environments and amongst healthcare practitioners who had direct contact with cases of SARS. The first outbreak of SARS actually occurred in the Chinese city of Guangzhou province in 2002 from where the world outbreak of the disease started from. Aside the lower respiratory tract of humans which SARS coronavirus is known to colonize, the virus also attack the gastrointestinal tract and neurological tissues of the body. The main routes via which coronaviruses are transmitted are via aerosols, body contact and through the oral-feacal route (especially for some toroviruses that infect animals).

But the main major route via which SARS coronaviruses are spread in human population is via the respiratory tract of infected individuals especially when they cough and sneeze. SARS coronavirus infection in humans has an incubation period of 2-7 days and infected individuals are highly infectious especially when they present with respiratory symptoms that characterize the disease. Common cold, malaise, and fever are some of the asymptomatic symptoms of SARS; and when individuals become very symptomatic, infected individuals have myalgia, dry throat and even shortness of breath. No specific antiviral therapy exists for the treatment of SARS in humans. However, the management of the disease is mainly based on supportive therapy.

SELECTED REFERENCES

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Alan J. Cann (2005). Principles of Molecular Virology. 4th edition. Elsevier Academic Press,   Burlington, MA, USA.

Alba R, Bosch A and Chillon M (2005). Gutless adenovirus: last-generation adenovirus for gene therapy. Gene Ther, Suppl 12:S18-S27.

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Barrett   J.T (1998).  Microbiology and Immunology Concepts.  Philadelphia,   PA: Lippincott-Raven Publishers. USA.

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