Climate exerts both direct and indirect effects on the appearance and spread of human and animal infectious diseases. The impact of climate change on the transmission and geographical distribution of vector-borne diseases, including zoonoses (infections transmissible between vertebrate animals and humans), has been associated with changes in the replication rate and dissemination of pathogen, vector and animal host populations, which are sensitive to changing temperature and rainfall. The available evidence indicates the potential for an increasing challenge to European public health from arboviral (arthropod-transmitted) diseases such as tick-borne encephalitis (TBE), West Nile fever (WNF), chikungunya, diseases caused by rodent-borne hanta viruses, and parasitic diseases such as dirofilariasis and leishmaniasis. Climate change is also increasing the threat of infections, such as bluetongue virus (BTV), in domesticated animals.

Although the evidence base is fragmented and it is also important to take account of the other various determinants of changes in ecosystems and in human, animal and microbial behaviour, the fundamental influence of climate change on infectious diseases in Europe is beginning to be discerned.