Hantavirus Emergence in Rodents, Insectivores and Bats: What Comes Next?

Hantaviruses have attracted increased public interest in recent years and are a clear example of an emerging virus. The enveloped virions of hantaviruses contain a tri-segmented single-stranded RNA genome of negative polarity. The initial discovery of hantaviruses dates back to investigations initiated after a large number of United Nations military personnel were affected by a severe disease during the Korean conflict in the 1950s. These investigations resulted in the discovery of Hantaan virus, the prototype species within the genus, in the striped field mouse (Apodemus agrarius). In the following years a large number of additional hantaviruses in other rodents were identified. The congruence in the phylogenetic relationship of the viruses and their rodent reservoirs was explained by a virus–host co-divergence. Further phylogenetic investigations and the discovery of novel hantaviruses indicated host-switch and subsequent host adaptation as an alternative evolution mechanism. In humans hantaviruses cause two disease syndromes, hemorrhagic fever with renal syndrome and hantavirus cardiopulmonary syndrome. Due to similarities in the disease symptoms it is currently suggested to unify both as “hantavirus disease.” For detection of hantavirus infections a broad spectrum of molecular and serological diagnostic methods exists. Problems for hantavirus diagnostics in patients arise from the short-termed viremia and the strong cross-reactivity of sera against the nucleocapsid protein, frequently used in serological assays. The geographical distribution of the hantaviruses follows the range of their reservoir rodents. Human pathogenic hantaviruses are most likely distributed world-wide, but so far with little evidence for their presence in Africa, and Australia in particular. The recent discoveries of novel hantaviruses in shrews, moles and even bats raise questions about the origin and molecular evolution of hantaviruses. Importantly, the consequences of these novel viruses for public health are still unknown. The emergence of hantaviruses might be driven by various factors. Changes in small mammal reservoir population dynamics represent one of the major drivers for the occurrence of disease clusters and outbreaks. Long-term monitoring studies of small mammal reservoirs are needed to develop and validate prediction models and to implement them in early warning tools. Future hantavirus studies will profit from the application of Next Generation Sequencing technique, and the development of a reverse-genetics system.