Table 2. Summary of laboratory results of confirmed human Usutu virus infection, Hungary, 2018.
| Serum sample analysis | |||||
|---|---|---|---|---|---|
| Immunofluorescence assay | |||||
| Anti-USUV IgG | 1:160 | Anti-WNV IgG | 1:20 | Anti-TBEV IgG | 1:10 |
| Anti-USUV IgM | 1:640 | Anti-WNV IgM | 1:40 | Anti-TBEV IgM | < 1:10; negative |
| Anti-USUV IgA | ≥ 1:1,280 | Anti-WNV IgA | 1:20 | Anti-TBEV IgA | < 1:10; negative |
| ELISA | |||||
| WNV IgM capture ELISA: index value = 4.75; positive | |||||
| Molecular diagnostic results | EDTA-treated whole blood | Urine | |||
| WNV RT-qPCR | Negative | Negative | |||
| USUV RT-qPCR | Positive Ct 37.00 | Negative | |||
| USUV nested RT-PCR | Positive | Negative | |||
EDTA: ethylenediaminetetraacetic acid; ELISA: enzyme-linked immunosorbent assay; TBEV: tick-borne encephalitis virus; USUV: Usutu virus; WNV: West Nile virus.
We used in-house developed indirect immunofluorescent assays for IgG, IgM and IgA detection of USUV, WNV and TBEV [26], a commercial ELISA (Focus Diagnostics, DiaSorin Molecular LLC, Cypress, United States) and an in-house developed quantitative RT-PCR [34]. Cut-off for antibody titres: <1:10: negative; ≥1:10: positive; 1:10: indeterminate. All samples were taken 10 days after symptom onset.