Flaviviviridae

The word “flavi” is latin for yellow because one of the most famous flaviviruses is Yellow Fever Virus. Viruses in the flavivirus family are all single-stranded RNA viruses with linear non-segmented genomes. Viruses in this family are considered positive (+) sense because proteins are made directly from the template strand of RNA which is present in the viral capsid. Production of a complementary RNA strand is not necessary for viruses in this family to produce protein. The genome of these viruses are on average 11,000 nucleotides long - they encode around 10 genes. The capsid of viruses in this family are icosahedral shaped and around the viral capsid a spherical shaped envelope is present. The capsids are approximately 40-50 nanometers in diameter and are composed of a single type of capsid protein.

Replication:

Replication of Flaviviruses takes place in the cytoplasm. Flavivirus cannot replicate in the nucleus because, like most other RNA viruses, it uses the host cell's RNA dependant RNA polymerase to replicate. Primarily, the virus will make a full length copy of the complementary, minus strand genome. This complementary genome then serves as a template strand for further replication. Over the course of replication, about ten plus strands accumulate for each negative template strand. It has been shown that in order for Flaviviridae viruses to replicate successfully they must have complementary binding regions on both the 3’ and the 5’ ends of the genome which allow cyclization of the genome to occur.

Proteins:

Flaviviridae has three structural proteins as follows: C/V2 are the capsid proteins, M/V1 are the matrix proteins and E/V3 are the envelope proteins and glycoproteins. Flaviviridae encodes seven non-structural proteins whose functions are not entirely designated by include protease, helicase, replicase and virion maturation.

Viruses in the Flavi genera are transmitted by arthropods, mainly mosquitoes and ticks. Flaviviruses that are transmitted by arthropods are known as Group B Arboviruses. "Arboviruses" (viruses transmitted by arthropods) include Yellow Fever Virus, Dengue Fever Virus, and Japanese Encephalitis Virus (see list below for full inclusion). Viruses in the Hepaci genera, Hepatitis C and Hepatitis G, are transmitted parenterally (through blood) as well as sexually and vertically (from mother to child).

Prevention Vaccines exist for both Yellow Fever Virus and Japanese Encephalitis. Both vaccines are inactivated and have proved highly efficacious in labs and clinics. For more information about vaccines see Timeline. Otherwise the best ways to prevent infection with arboviruses are behavioral, such as using mosquito nets, bug repellent and protective clothing. With hepatitis viruses, behavioral preventative measures such as protected sex, refraining from injection drug use, and proper disposal of needles is suggested. Any blood or products that have come into contact with blood should be handled with utmost caution.