Flavivirus

Flavivirus is a genus of the family Flaviviridae. This genus includes the West Nile virus, dengue fever virus, tick-borne encephalitis virus, yellow fever virus, Zika virus, and several other viruses which may cause encephalitis (swelling in the brain).

Flaviviruses are named for the yellow fever virus - "flavus" means "yellow" in Latin.  (Yellow fever was named because it often caused yellow-colored skin, called jaundice, in its victims.)

Flaviviruses share a common size (40-65 nm) and symmetry (shape), and they look similar under an electron microscope.  They are made of single-stranded RNA.

Humans get these viruses after being bitten by an infected mosquito or tick.  Usually, if a human who has a Flavivirus gets bitten by a healthy mosquito or tick, the human will not have enough of the virus in their blood to infect the insect.  This means humans do not help continue the virus's life cycle (by infecting insects who go on to infect other people).  However, this is not true for yellow fever or dengue fever.

People can also get Flaviviruses in other ways, like:
 Touching the dead bodies of animals who had a Flavivirus
 Getting a blood transfusion from someone who has a Flavivirus
 Having sex with someone who has a Flavivirus: this has been proven true at least for the Zika virus.
 Drinking unpasteurized milk products
 A fetus can get a Flavivirus from its mother during childbirth
It is not likely that animals can spread Flaviviruses directly to humans.  Scientists believe that an mosquito or tick has to bite an infected animal before it can spread the virus to a human by biting that human.  This means that Flaviviruses are probably not contagious diseases.  For example, early tests with yellow fever showed that the disease is not a contagious disease.

References

category:Viruses