In Search for Factors that Drive Hantavirus Epidemics

Abstract

In Europe, hantaviruses (Bunyaviridae) are small mammal-associated zoonotic and emerging pathogens that can cause hemorrhagic fever with renal syndrome (HFRS). Puumala virus, the main etiological agent carried by the bank vole Myodes glareolus is responsible for a mild form of HFRS while Dobrava virus induces less frequent but more severe cases of HFRS. Since 2000 in Europe, more than 3000 cases of HFRS have been recorded, in average, each year, which is nearly double compared to the previous decade. In addition to this upside long-term trend, significant oscillations occur. Epidemic years appear, usually every 2–4 years, with an increased incidence, generally in localized hot spots. Moreover, the virus has been identified in new areas in the recent years. A great number of surveys have been carried out in order to assess the prevalence of the infection in the reservoir host and to identify links with different biotic and abiotic factors. The factors that drive the infections are related to the density and diversity of bank vole populations, prevalence of infection in the reservoir host, viral excretion in the environment, survival of the virus outside its host, and human behavior, which affect the main transmission virus route through inhalation of infected rodent excreta. At the scale of a rodent population, the prevalence of the infection increases with the age of the individuals but also other parameters, such as sex and genetic variability, interfere. The contamination of the environment may be correlated to the number of newly infected rodents, which heavily excrete the virus. The interactions between these different parameters add to the complexity of the situation and explain the absence of reliable tools to predict epidemics. In this review, the factors that drive the epidemics of hantaviruses in Middle Europe are discussed through a panorama of the epidemiological situation in Belgium, France, and Germany.

Seroprevalence of hantavirus infections in Switzerland in 2009: difficulties in determining prevalence in a country with low endemicity

“…Some recreational/leisure or work-related activities are known to be risk factors for PUUV infection [36][37][38]; but this was not found in our study. Travel to other endemic countries, such as in Asia or south-east Europe, was also not found to increase risk.…”

“…On the basis of prevalence data from a study performed in the north-eastern part of Switzerland in 2002-03, we investigated predominantly young soldiers as a potential risk group, but since their military service did not take place during a year of increased hantavirus activity in regions close to Switzerland, they were not at particular risk of infection [4,27,38]. Due to time-consuming preparatory work, the period of blood collection in the military personnel could not be handled flexibly and could not be postponed to the following year: in that year, increased numbers of hantavirus infections were documented in Germany [4,11].…”

Spatial and temporal variation of hantavirus bank vole infection in managed forest landscapes

“…In Belgium, Linard et al (2007b) found that infected bank voles were common in the parts of the country that had a large proportion of broad-leaved forests. In Germany, habitat structures associated with old forests such as dead wood was linked to increased probability of PUUV in bank voles within homogenous forest landscapes (Heyman et al 2012, Thoma et al 2014. Also, bank voles in wooded recreation areas and forested city parks were found to have high PUUV prevalence (Essbauer et al 2007, Ulrich et al 2008.…”

Surface Temperatures at the Continental Scale: Tracking Changes with Remote Sensing at Unprecedented Detail

“…Late frost events in spring may have a significant damaging impact on plants and lead to an economic loss in agriculture [40]. Additionally, late frost is considered to be an abiotic factor triggering tree mast [41], which, in turn, leads to high rodent densities and, subsequently, to Hantavirus epidemics, as observed in temperate Europe [42].…”