Table. Laboratory results confirming WNV infection of 73-year-old woman, Greece, 2012*†.
| Sample | Date | RT-PCR (Ct value) | WNV ELISA IgM (ratio) | WNV ELISA IgG (ratio) | Flavi IFAT IgM | Flavi IFAT IgG |
|---|---|---|---|---|---|---|
| Serum | Aug 15 | Positive (45.47) | Positive (25) | Negative | ND | ND |
| CSF | Sep 3 | ND | Positive (5.16) | Positive (2.21) | ND | ND |
| Serum | Sep 6 | Positive (42.87)‡ | Positive (4.76) | Positive (2.63) | WNV positive | WNV positive§ |
*WNV, West Nile virus; RT-PCR, reverse transcription PCR; Ct, cycle threshold; Flavi, flavivirus; IFAT, indirect fluorescent antibody technique; ND, not done; CSF, cerebrospinal fluid. †The ELISA is positive if ratio >1.1 for IgM and >1.5 for IgG. The cutoff value for IFAT is 1/10 for both IgG and IgM. ‡Sequencing revealed a 116-bp sequence perfectly matched to the WNV amplicon and is highly suggestive for WNV lineage 2 on the basis of the presence of 2 specific nucleotides. §Strongest signal for WNV, weak signal for other flaviviruses (Japanese encephalitis virus, dengue viruses 1–4, yellow fever virus).