“…In previous reports, EEEV IgM was detected as early as 1 day after the onset of symptoms, peaks 1-3 weeks after the onset of illness, and may remain positive for up to 3 months (Calisher et al, 1986a,b). The patient in this study had onset of encephalitis symptoms on DOI 7 (Pouch et al, 2018), making the observed decline in IgM between DOI 39 and DOI 48 consistent with a peak titer occurring in the first 3 weeks after symptom onset. Unfortunately, residual cerebrospinal fluid (CSF) samples were not available for testing from this EEEV patient to document the longitudinal course of CSF antibody production, although clinical testing revealed a positive CSF IgM antibody test on DOI 9 (Pouch et al, 2018).…”