Viruses can evolve faster than mammals by many orders of magnitude,
being near instantaneous compared to the scale of mammalian
adaptation over years and decades. This may be less so for arthropodtransmitted
viruses where the generation time of the vector is measured
in weeks if not days. Thus emergence of vector-borne diseases
represent a major threat in the short term once conditions for adaptation
result in emergence and an extension of host range as a consequence,
as was the case for chikungunya virus in 2005.5