Jamestown Canyon virus

Jamestown Canyon encephalitis is an infectious disease caused by the Jamestown Canyon virus, an orthobunyavirus of the California serogroup. It is mainly spread during the summer by different mosquito species in the United States and Canada. The virus is one of a group of mosquito-borne or arthropod-borne viruses, also called arboviruses, that can cause fever and meningitis or meningoencephalitis, mostly in adults. Jamestown Canyon virus disease is relatively rare; in the United States, the CDC found only 31 disease cases from 2000 to 2013, but it is likely under-recognized and probably endemic throughout most of the United States. About 2 days to 2 weeks after the bite of an infected mosquito disease symptoms of a nonspecific summertime illness with sore throat, runny nose and cough, followed by fever, headache, nausea and vomiting can develop. Neuroinvasive disease occurs in two thirds of reported cases and is characterized by severe headache and neck stiffness as in meningitis or increasing lethargy and altered mental status up to coma as in meningoencephalitis. No acute flaccid paralysis, no death and no acquisition from a blood transfusion has ever been reported. The Jamestown Canyon virus is an orthobunyavirus and was first isolated in 1961 from Culiseta mosquitoes in Jamestown, Colorado. Since then it has been found in Aedes, Coquillettidia perturbans, Culex, Culiseta and Ochlerotatus species in northern states of the mainland US, in various mammals throughout mainland North America, and identified in humans throughout the United States. The virus is transmitted in saliva to a vertebrate host when an infected mosquito takes a blood meal. It thus cycles between mosquito and vertebrate amplifier hosts, mainly white-tailed deer. In a study from Newfoundland, JCV was significantly associated with large mammals such as sheep, cattle and horses. In Michigan and Ontario moose and bison are believed to be the primary reservoir. The virus winters in mosquito eggs, which it reaches by transovarial transmission.The female mosquito lays eggs that carry the virus, and the offspring can transmit the virus to deer or ruminants and humans. Infected mosquitoes were found equally distributed throughout the state of Connecticut, irrespective of land use. The full genome has been sequenced. The authors found a relatively high level of amino acid sequence conservation from viruses isolated 57 years apart 'indicating that the virus is in relative evolutionary stasis'. They also found JCV to be genetically similar to Inkoo virus in Northern Europe (Finland, Sweden), 'suggesting that much of the northern hemisphere contains JCV or similar variants'.The negative sense RNA genome is in three segments. The L segment encodes the L endonuclease (an RNA-dependent RNA polymerase enzyme) for genome replication and mRNA synthesis. The M segment encodes a polyprotein, further cleaved in the Gn and Gc surface glycoproteins for attachment and the NSm nonstructural protein that influences virulence. The S segment encodes the NSs protein for immune suppression and virulence, and the N structural nucleocapsid protein.