BUNYAVIRIDAE FAMILY

Bunyaviridae family comprises of viruses that infect humans, animals and even plants. The main viral genera that make up the Bunyaviridae family are Orthobunyavirus, Phlebovirus, Nairovirus, and Hantavirus genera (which all infect animals) and the genera Tospovirus (which infect plants). Majority of viruses in the Bunyaviridae family are arthropod-borne viruses because they are transmitted by arthropods especially blood-sucking insects such as mosquitoes and ticks. Viruses that are transmitted via arthropods or insects to humans are generally known as arboviruses. Viruses in this family have a helical nucleocapsid and they are enveloped viruses. They replicate in the cytoplasm and they are released from their host cell via cytoplasmic membrane by a budding process. The viruses in Bunyaviridae family measure between 80 to 120 nm in diameter.

Bunyaviruses have a ss(-)RNA genome. The viruses that cause infection in humans are found in the genera Orthobunyavirus (e.g. La Crosse virus), Nairovirus (e.g. Crimean-Congo haemorrhagic fever virus) and Phlebovirus (e.g. Sandfly Fever Sicilian virus). Generally, the viruses in the Bunyaviridae family that infect humans cause haemorrhagic fever; and they can also be referred to as hemorrhagic fever viruses as is applicable to Ebola and Lassa fever viruses. The infections caused by Bunyaviruses are usually benign, and they are characterized by febrile infections that include haemorrhagic fevers. In severe cases of the disease, the central nervous system (CNS) may also be affected. Orthobunyaviruses causes benign forms of encephalitis; Nairoviruses causes haemorrhagic fevers; Phleboviruses causes sandfly fever or phlebotomous fever; and Hantaviruses causes Hantavirus pulmonary syndrome (HPS) in humans. All the genera of Bunyaviridae family that cause infections in humans with the exception of Hantavirus genera are transmitted to humans via arthropods.

Hantaviruses are transmitted to humans through rodents such as mice and rats. And a human infection with Hantaviruses (which is notorious in causing haemorrhagic fevers in humans) is through the inhalation of aerosols from the excreta or body secretions (e.g. urine, saliva and feaces) of these animals that harbour the virus. Such transmission of viruses from rodents to humans is generally known as an aerogenical transmission. Rodents are the natural reservoirs of Hantavirus, and they remain apathogenic in these animals (i.e. they do not cause infections in them). However, they cause serious infections in humans when they are aerogenically transmitted to humans. Prevention of infections caused by Bunyaviruses is through avoidance of contact with rodents and insect bites.

SELECTED REFERENCES

Acheson N.H (2011). Fundamentals of Molecular Virology. Second edition. John Wiley and Sons Limited, West Sussex, United Kingdom.

Ahmad K (2002). Norwalk-like virus attacks troops in Afghanistan. Lancet Infect Dis, 2:391.

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.

Alberts B, Bray D, Johnson A, Lewis J, Raff M, Roberts K and Walter P (1998). Essential Cell Biology: An Introduction to the Molecular Biology of the Cell. Third edition. Garland Publishing Inc., New York.

Balows A, Hausler W, Herrmann K.L, Isenberg H.D and Shadomy H.J (1991). Manual of clinical microbiology. 5th ed. American Society of Microbiology Press, USA.

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

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