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.
[1] 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.
[3][4] The virus is transmitted in saliva to a vertebrate host when an infected mosquito takes a blood meal.
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.
Similarly, the New York State Department of Health has performed JCV plaque reduction neutralization tests since 2000 on samples positive for California serogroup IgG antibodies.
[2] No specific therapy exists for arboviral infections; treatment is limited to supportive care and managing complications, such as relieving increased intracranial pressure.
[5] In the latest US review covering 2000–2013, more than half of cases were identified in 2013 alone, the first year the CDC implemented routine JCV IgM antibody testing.
[3] Historically, most cases of encephalitis reported to the CDC occurred in the north of the mainland United States.
[3] However, for 2013, dates of illness onset ranged from January through November, with 14 (64%) of the 22 cases occurring during July until September.