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Features of Flavivirus

Dr Sampurna Roy MD





The Flaviviridae include almost 70 viruses, nearly half of which have been associated with human disease.

Flavivirus is a genus of the family Flaviviridae.

Flavivirus share a common size (40-60 nanometres), symmetry (enveloped, icosahedral nucleocapsid), nucleic acid (positive-sense, single stranded RNA approximately 10,000-11,000 bases), and appearance in the electron microscope.

These viruses are among the most important arthropod-borne viruses worldwide and include dengue, yellow fever, and Japanese encephalitis viruses.

Morbidity and mortality caused by these viruses vary, but collectively they account for millions of encephalitis, hemorrhagic fever, arthralgia, rash, and fever cases per year.

Most of the members of this family are transmitted between vertebrate hosts by arthropod vectors, most commonly mosquitoes or ticks.

Transmission cycles can be simple or complex depending on the hosts, vectors, the virus, and the environmental factors affecting both hosts and viruses.


Mosquito-Borne Viruses:


-Dengue Virus



-Yellow Fever Virus


-Japanese encephalitis virus



-St. Louis Encephalitis Virus



-Murray Valley encephalitis virus



-West Nile Virus




Tick-Borne Viruses:


- Tick-borne encephalitis virus

- Omsk hemorrhagic fever virus

- Kyasanur Forest disease virus



Further reading:

Tick-borne flaviviruses.Adv Virus Res. 2003;61:317-71

Tick-borne encephalitis (TBE), one of the most dangerous neuroinfections in Europe and Asia, is caused by tick-borne encephalitis virus (TBEV) and currently involves approximately 11,000 human cases annually, mostly in Russia. This chapter describes the main problems associated with the epidemiology, ecology, pathogenesis, and control of this disease. We have attempted to review the factors that influence the incidence and distribution of TBE, and to discuss possible reasons for the different clinical manifestations including most commonly observed asymptomatic infections, fever forms, acute encephalitis, and the less frequently registered biphasic milk fever and chronic encephalitis. Epidemiologic data concerning the other tick-borne flaviviruses, namely Louping ill virus, Langat virus, and Powassan virus that also produce encephalitis on a smaller scale, are also presented. Here we describe the history and current epidemiological role of Omsk hemorrhagic fever virus and Kyasanur forest disease virus, two viruses that are genetically closely related to TBEV, but produce hemorrhagic fever instead of encephalitis, and provide possible explanations for these differences. The other viruses in the tick-borne flavivirus group are also included despite the fact that they do not play an essential epidemiologic role in humans. This chapter contains a brief history of vaccination against TBE including the trials with live attenuated vaccine and reviews the modern trends in development of vaccine virus strains.






Dr Sampurna Roy  MD

Consultant  Histopathologist (Kolkata - India)


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