Flavivirus Infections in Humans

Abstract

Abstract Flaviviruses are enveloped, positive‐stranded ribonucleic acid viruses that are globally emerging and cause significant human disease in the form of encephalitis or haemorrhagic fever. The medically important flaviviruses are dengue, yellow fever, Japanese encephalitis, St. Louis encephalitis, tick‐borne encephalitis (TBE) and West Nile viruses. Most flaviviruses are maintained in animal reservoirs in nature and are transmitted to humans primarily through the bite of an infected mosquito or tick. Human‐to‐human transmission can also occur through transfusion or transplantation of infected tissue. Vaccines are available for only yellow fever and Japanese and TBE; however, new vaccines for dengue and West Nile are in clinical trials in humans. Disease diagnosis can be difficult as all flaviviruses are antigenically and genetically closely related. There are no effective antiviral therapies that exist for any flavivirus so the main approach to disease control is through vaccination and vector control. Key Concepts: Flaviviruses are important global human pathogens that primarily cause encephalitis and haemorrhagic disease. Flaviviruses are enveloped, positive‐stranded RNA viruses. Most human flaviviral infections are asymptomatic. Flaviviruses are primarily transmitted to man by the bite of an infected mosquito or tick and are maintained in nature in animal reservoirs. Flaviviruses can also be transmitted between humans by transfusion or transplantation of contaminated tissue. All flaviviruses are closely related so diagnosis of human disease can be difficult. Most flaviviral diseases are considered emerging infections. There are no effective drugs or treatments for flaviviral infections. Approved human flaviviral vaccines are available for Japanese encephalitis, tick‐borne encephalitis and yellow fever. Control of flavivirus outbreaks largely depend on vector‐control measures.