Arbovirus persistence in North-Western Europe: Are mosquitoes the only overwintering pathway?

In some areas in temperate Europe, genomic analyses of mosquito-borne virus outbreaks have revealed the presence of similar virus strains over several years, indicating local overwintering of these viruses. However, it remains unclear how mosquito-borne viruses can persist in winter, when conditions are generally unfavourable for virus circulation. One of the presumed routes of virus persistence is via diapausing mosquitoes. Here, we set out to study whether arbovirus persistence of West Nile virus (WNV), Usutu virus (USUV) and Sindbis virus (SINV) occurs in diapausing mosquitoes in the Netherlands. To this end, mosquito collections were carried out in the winter of 2020 and 2021, in hibernacula located in two areas with previously observed WNV and/or USUV activity. In total, we collected 4200 mosquitoes belonging to four species (Culex pipiens, Culiseta annulata, Anopheles maculipennis s.l., and Culex territans), which were pooled in 490 monospecific pools. These pools were subjected to WNV-, USUV- and SINV-screening using a multiplex real-time RT-PCR assay. All mosquito pools tested negative for the presence of WNV, USUV and SINV RNA. Consequently, we did not find evidence of arbovirus persistence in diapausing mosquitoes in the Netherlands, even though USUV and WNV have re-appeared in birds and/or mosquitoes during the summer seasons of 2020-2022. Concluding, given the persistence of USUV and WNV in the Netherlands and SINV in other temperate regions, this study highlights the importance of further research on (alternative) arbovirus overwintering routes.

Highly Divergent SARS-CoV-2 Alpha Variant in Chronically Infected Immunocompromised Person.

We detected a highly divergent SARS-CoV-2 Alpha variant in an immunocompromised person several months after the latest detection of the Alpha variant in the Netherlands. The patient was infected for 42 weeks despite several treatment regimens and disappearance of most clinical symptoms. We identified several potential immune escape mutations in the spike protein.

Comparison of commercial realtime reverse transcription PCR assays for the detection of SARS-CoV-2.

The emergence of a new coronavirus in Wuhan China has triggered a global need for accurate diagnostic assays. Initially, mostly laboratory developed molecular tests were available but shortly thereafter different commercial assays started to appear and are still increasing in number. Although independent performance evaluations are ongoing, available data is still scarce. Here we provide a direct comparison of key performance characteristics of 13 commercial RT-PCR assays. Thirteen RT-PCR assays were selected based on the criteria that they can be used following generic RNA extraction protocols, on common PCR platforms and availability. Using a 10-fold and 2-fold dilution series of a quantified SARS-CoV-2 cell-cultured virus stock, performance was assessed compared to our in house validated assay. Specificity was tested by using RNA extracted from cultured common human coronaviruses. All RT-PCR kits included in this study exhibited PCR efficiencies > 90%, except for the Sentinel Diagnostics B E-gene RUO assay (80%). Analytical sensitivity varied between 3.3 RNA copies to 330 RNA copies. Only one assay cross reacted with another human coronavirus (MERS). This study provides a technical baseline of 13 different commercial PCR assays for SARS-CoV-2 detection that can be used by laboratories interested in purchasing any of these for further full clinical validation.