Flaviviruses

Categorization
Genome: RNA Virus, Positive ssRNA Virus Structure: Enveloped Virus
Overview
  • Flavirviruses are a family of nearly 70 structurally-related viruses which are transmitted to humans by arthropods and generally cause encephalitis] along with other pathologies. Hepatitis C Virus is likely a type of Flavivirus but is not transmitted by arthropod vector and is considered separately (see page). We discuss prominent members of this family individually below.
Yellow Fever
  • Transmission
    • Yellow Fever occurs in tropical area's of South America and Africa. The virus is transmitted to humans via infected mosquitoes.
  • Clinical Consequences
    • Nearly a week after inoculation the patient develops an abrupt onset of intense constitutional symptoms including a high fever, headache, and myalgia, especially causing back pain. Most people recover but a minority of patients progress to develop viral hepatitis which manifests as jaundice. In those whose liver's are affected, hepatic failure is rare but can occur.
Dengue Fever
  • Transmission
    • Dengue Fever occurs in tropical area's and is spread by infected mosquitoes.
  • Clinical Consequences
    • In most individuals acute onset of constitutional symptoms occurs characterized by fever and myalgias. Arthralgias, back pain, and deep bone pain have given Dengue Fever the moniker of "Break-bone Fever". In a minority of individuals the fever progresses to a syndrome termed "Dengue Hemorrhagic Shock" in which substantially increased vascular permeability results in hypovolemic Shock and in some cases widespread hemorrhage.
    • FYI: It is thought that individuals who develop Dengue Hemorrhagic Shock possess antigen-specific but non-neutralizing antibodies to the virus due to previous infection with a similar but non-identical serotype of the virus. Through unclear mechanisms it is thought that virus-antibody complexes promote secretion of enormous amounts of cytokines which results in the increased vascular permeability and hemorrhage characteristic of the syndrome.
Japanese B Encephalitis
  • Transmission: Japanese B Encephalitis Virus is spread by infected mosquitoes and occurs in Asia
  • Clinical Consequences: Encephalitis with nearly a third of infections being fatal
West Nile Virus
  • Transmission
    • West Nile Virus is spread by infected mosquitoes. It was originally more common in Middle East, Africa, and Asia, but has since spread to the United States.
  • Clinical Consequences
    • In the vast majority of cases, West Nile Virus infection is asymptomatic or causes a mild flu-like illness. In a small minority of individuals, Encephalitis and Meningitis may result.