Commentary: Development of a Comparative European Orthohantavirus Microneutralization Assay With Multi-Species Validation and Evaluation in a Human Diagnostic Cohort.

In this otherwise excellent article (Hoornweg et al., 2020) cited “Three human SEOV infections were confirmed, of which one was previously described as the first [2018] proven SEOV case in The Netherlands, based on IFT [immuno-fluorescence test] serology and an epidemiological link to SEOV RNA-positive [wild] rats) (Swanink et al., 2018), and now confirmed by comparative VNT [virus neutralization test].” This is historically incorrect: 27 years before Swanink et al, Groen et al. already reported wild rat-induced human SEOV infections in The Netherlands, moreover, in the same Dutch Institute of Public Health and Environmental Protection, Bilthoven, and with the same IFT (or IFA) technique (Groen et al., 1991). In addition, this 1991 report compared 14 non-laboratory cases of hemorrhagic fever with renal syndrome (HFRS), caused by the common European arvicolid orthohantavirus Puumala (PUUV), to 13 cases infected by the then rare (at least in early 1990s Western literature) orthohantavirus Seoul (SEOV), a juxtaposition in one single paper of two different local Dutch pathogenic orthohantaviruses, thus constituting at that moment the earliest such confrontation in nascent Western hantavirus literature (Figure 1). Moreover, not only 11 Dutch and/or Belgian laboratory rat-induced early 1980s SEOV-HFRS cases were detected, but also two wild rat-induced cases (arrows in Figure 1), thereby scoring yet another “first” in western hantavirus literature. Open in a separate window Figure 1 IFA: immuno-fluorescence assay or immuno-fluorescence test (IFT). ELISA, enzyme-linked immunosorbent assay. CTB ELISA, complex-trapping blocking, an inhibition ELISA variant. Closed circles: 1980s laboratory rat-acquired human hantavirus infections. Open circles: non-laboratory rat-acquired or “wild” human hantavirus infections, mostly being 1980s PUUV-induced, except for two “wild” cases (arrows), being 1980s wild rat-induced SEOV infections. Thick arrow: Dutch farmer, thin arrow: Belgian homeless vagabond, both with wild rat-exposure. In these two cases, SEOV infection was missed in IFA, showing surprisingly high cross-reacting PUUV titers (A), but confirmed, albeit with lower titers, in ELISA (B), and unmistakably ascertained in CTB-ELISA (C). Consequently, these two cases would have been mistaken for PUUV infections, if relying only on IFT/IFA. Adapted from Groen et al., 1991. Copyright © 1991 Wiley‐Liss, Inc., A Wiley Company.