Am J Trop Med Hyg 93:384C389. and approximately half of patients require hospitalization. Interestingly, neuroinvasive disease is present in 54% of reported cases of JCV, but unlike disease caused by WNV, acute flaccid paralysis associated with JCV has not been observed (3). No deaths associated with JCV have been reported. JCV predominantly affects adults, although cases in children have been reported (3). Patients with JCV are managed with supportive care, as no specific therapy PIM-1 Inhibitor 2 or vaccination is currently available. JCV infection is likely underdiagnosed due to lack of awareness of this computer virus and limited diagnostic screening options. The laboratory diagnosis of JCV is usually accomplished using serology, while other methods, such as nucleic acid amplification assessments (e.g., real-time PCR) and viral culture, are not routinely performed. In 2013, JCV IgM antibody screening was implemented at the CDC; however, confirmatory screening for JCV must typically be requested by a state health department based on preliminary results and/or exposure history. Confirmatory screening PIM-1 Inhibitor 2 includes anti-JCV IgM antibody screening, with a reflex to PRNT if reactive (3). Seroprevalence studies have demonstrated the presence of neutralizing antibodies to JCV at numerous rates (3.9 to 17.6% in two studies [5, 6]), which suggests that mild or asymptomatic infections occur. Serologic screening for JCV is usually complicated by significant cross-reactivity with other viruses in the California serogroup, as was observed in our patient during screening at both MDH and initial EIA testing at the CDC (Table 1). Previous studies using the Rabbit polyclonal to ALKBH1 JCV IgM EIA exhibited that 46% of patients with JCV contamination test positive PIM-1 Inhibitor 2 for LACV IgM, while 15% have inconclusive results (3). Therefore, screening by PRNT is required to establish a definitive diagnosis of JCV and LACV. The CDC performs PRNT for multiple closely related viruses and compares the endpoint neutralizing antibody titers between them. The infectious computer virus is typically identified as the one with at least a 4-fold or higher endpoint titer compared to the other tested viruses. In our case, the JCV serum PRNT endpoint titer was high at 1:2,560 (reference range, 1:10), although PRNT titers of 1 1:20 were observed for both SSHV and LACV. Interestingly, PRNT on our patient’s CSF specimen was positive for JCV (endpoint titer, 1:16) but unfavorable for LACV. As highlighted in this case, considerable serologic screening is usually often required to establish a diagnosis of JCV contamination. Our individual required serologic screening on serum and CSF, using multiple methods (e.g., EIA, IFA, and PRNT) performed at three laboratories (Mayo Medical center, MDH, and CDC) to confirm the diagnosis and rule out other arbovirus infections. In summary, we present a case of a 10-year-old lady with meningoencephalitis caused by JCV. She recovered from her illness without long-term sequelae. JCV is likely an underdiagnosed viral contamination that health care providers and clinical laboratory professionals should consider. Specifically, contamination with JCV should be included in the differential diagnosis of patients with mosquito exposure who present with a central nervous system contamination or flu-like illness in the spring to early fall. It is important to be aware that contamination with JCV may result in serologic cross-reactivity with other more common arboviruses (e.g., LACV), and atypical serology results (e.g., atypical staining by IFA, poor positivity by multiple arboviral PIM-1 Inhibitor 2 screening assessments) may prompt specific screening for JCV. Currently, laboratory screening for JCV may be facilitated through select state health departments and the CDC. SELF-ASSESSMENT QUESTIONS Contamination with JCV may result in serologic cross-reactivity with which of the following viruses? La Crosse computer virus Cytomegalovirus Enterovirus Powassan computer virus Which of the following statements about JCV is true? Infections most commonly occur between October and March in the United States Transmission has been documented for several different species of mosquito vectors Laboratory diagnosis of JCV is usually most commonly made by real-time PCR, with confirmation requiring growth of the computer virus in cell culture Vaccination for JCV is recommended in the United States for all those adults 18 to 65 years of age Which of the following methods is used to confirm a diagnosis of JCV contamination? IgM enzyme immunoassay Plaque reduction neutralization test IgM immunofluorescence assay NS1 antigen For answers to the self-assessment questions and take-home points, observe https://doi.org/10.1128/JCM.00255-18 in this issue. ACKNOWLEDGMENTS.