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

Transovarial transmission in field caught mosquitoes identifies a mechanism for the establishment of Usutu virus in a temperate country

“…While USUV is emerging across Europe and is considered endemic in many countries, detection of overwintering flaviviruses in diapausing mosquitoes is rarely recorded (16,22). Since mRNA expression during diapause is reduced and a transcriptional program leads to metabolic repression (23,24), it is likely that viral RNA is maintained at low titres in mosquito cells until conditions for replication become favourable.…”

“…Both maintenance of infection in diapausing adult mosquitoes and vertical transmission to larvae could be required for overwintering viral persistence in temperate areas. However, there has so far been no detection of virus in wild diapausing mosquitoes or in developing progeny (16).…”

A One Health approach to predict, monitor and prevent arbovirus infections, an extensive case study from the Netherlands - Editorial

“…These findings underscore the notion that disease risk is not homogeneously distributed across the landscape, and that variation in local land use and climate are important determinants of mosquito abundances and thereby also likely determinants for disease risk. Mosquito abundance and virus presence during winter were further investigated by Blom et al to assess their possible role in carry-over of a commonly present arbovirus that mainly affects birds (Usutu virus) [ 16 ]. Contrary to expectations, and despite re-emergence in the summers after, they did not detect any infected overwintering mosquitoes [ 9 ].…”