Viruses in Flavi genera are transmitted by arthropods, mainly mosquitoes and ticks. Flaviviruses that are transmitted by arthropods are known as Group B Arboviruses. Arboviruses include Dengue fever,yellow fever and west nile.

Major diseases caused by the Flaviviridae family include:
- Dengue Fever

- Yellow Fever

- West nile Encephalitis

Dengue fever is the most common flavivirus infection among humans. The incidence of disease corresponds to the worldwide dispersion of the principal vector, A aegypti, which serves to maintain the virus in a human-mosquito-human cycle.Epidemiologic patterns are highly varied but may be described as epidemic, endemic, or hyperendemic. In endemic regions, dengue fever occurs principally in children and often is unrecognized. In Southeast Asia where all four serotypes are continuously transmitted, epidemics of dengue hemorrhagic fever are a major cause of death among children, involving thousands of cases and a 3 to 10 percent case fatality rate.

After being bitten by a mosquito carrying the virus, the incubation period ranges from three to 15 days before the signs and symptoms of dengue appear. Dengue starts with chills, headache, pain upon moving the eyes, and low backache. Painful aching in the legs and joints occurs during the first hours of illness. The temperature rises quickly as high as 40° C, with relative low heart rate and low blood pressure. The eyes become reddened. A flushing or pale pink rash comes over the face and then disappears. The glands (lymph nodes) in the neck and groin are often swollen.

Fever and other signs of dengue last for two to four days, followed by rapid drop in temperature with profuse sweating. This precedes a period with normal temperature and a sense of well-being that lasts about a day. A second rapid rise in temperature follows. A characteristic rash appears along with the fever and spreads from the extremities to cover the entire body except the face. The palms and soles may be bright red and swollen.

Because dengue is caused by a virus, there is no specific medicine or antibiotic to treat it. For typical dengue, the treatment is purely concerned with relief of the symptoms. Rest and fluid intake for adequate hydration is important.

Yellow Fever is caused by a virus and spread to humans by the bite of an infected mosquito. The virus causes sudden onset of fever, four days after the bite. Most cases are mild, last less than a week, and the person makes a full recovery. Sometimes it is more serious. The liver may be damaged leading to jaundice - a yellowish tinge to the skin. Hence the name 'yellow' fever. It may cause joint pain and vomiting.

The initial or "acute" phase is normally characterized by high fever, general muscle pain, backache, shivers, headache, loss of appetite, nausea, and vomiting. Most patients improve and their symptoms disappear after three to four days. About 15 percent of those infected enter a "toxic" phase. In this phase, high fever reappears and can lead to shock, bleeding (from mouth, nose, eyes, and/or stomach), and kidney and liver failure.

Liver failure causes jaundice (yellowing of the skin and the whites of the eyes), which gives yellow fever its name. About half of the patients in the toxic phase die within 10 to 14 days. Persons recovering from yellow fever have lifelong immunity against reinfection.

West Nile virus is a mosquito-borne virus that can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord). It is to humans by the bite of an infected mosquito. A mosquito becomes infected by biting a bird which carries the virus. West Nile virus is not transmited by person-to-person contact such as touching, kissing, or caring for someone who is infected.

Most people who were infected with the West Nile virus had no symptoms or experienced mild illness with fever, headache and body aches before fully recovering. some people also developed a mild rash or swollen lymph glands. In some individuals, particularly the elderly, West Nile virus can cause serious disease that affects brain tissue. At its most serious, it can cause permanent neurological damage and can be fatal. Encephalitis (inflammation of the brain) symptoms include the rapid onset of severe headache, high fever, stiff neck, confusion, loss of consciousness, and muscle weakness. Death may occur in some instances.

There is no specific treatment for West Nile encephalitis other than supportive therapy for severe cases. Antibiotics will not work because a virus, not bacteria, causes West Nile disease. Currently no vaccine for the virus is currently available