Table 2. Three routes of introduction of exotic mosquito-borne pathogens into Canada.

Consideration	Local movement	Global movement, vector(s) present	Global movement, vector(s) absent
Emergence arising from local or global movement	Short-distance movement at the local scale	Long-distance movement at the global scale	Long-distance movement at the global scale
How geographic emergence may occur in Canada	Natural and regular movements of vectors/reservoirs/humans from a neighbouring endemic region	International travel, trade/transportation and migration of vectors/reservoirs/humans from a distant endemic region	International travel, trade/transportation and migration of vectors/reservoirs/humans from a distant endemic region
Pathogen	Present in a neighbouring endemic region (i.e., bordering a US state) but not in Canada	Present in a distant endemic region but not in Canada	Present in a distant endemic region but not in Canada
Vector mosquitoes present	Yes	Yes	No
Impact of climate change on of emergence	Amplify the natural transmission cycle and increase the likelihood of contact between vectors/reservoirs/humans in Canada	Amplify the natural transmission cycle and increase the likelihood of contact between vectors/reservoirs/humans in Canada and in the country of origin Pathogen must be imported into Canada via infected mosquitoes or viraemic humans/reservoirs (driven primarily by global movement and partially by climate change)	Amplify the natural transmission cycle and increase the likelihood of contact between vectors/reservoirs/humans in Canada and in the country of origin Pathogen must be imported into Canada via infected mosquitoes or viraemic humans/reservoirs (driven primarily by global movement and partially by climate change)
Current disease presentation in Canada	Travel-acquired cases from the US	Travel-acquired cases from the US and globally	Travel-acquired cases from the US and globally
Diseases that may emerge in Canada with climate change	SLEV and LCEV virus via established Cx. tarsalis/pipiens/restuans (SLEV) and Ae. triseriatus (LCEV) populations (73)	CHIKV via the emergence of Ae. albopictus in Canada (20) or malaria via established An. freeborni and An. quadrimaculatus populations (19)	JE, Rift Valley fever and other exotic MBDs where a natural competent vector is not present in Canada (Table 1)
Anticipated disease emergence in Canada with climate change	Locally-acquired cases High possibility of becoming endemic over time	Increase in travel-acquired cases Autochthonous cases or short-lived autochthonous outbreaks transmitted by emerging or established vector populations Possibility of becoming endemic over time	Increase in travel-acquired cases, but no further local mosquito-borne transmission

Abbreviations: Ae., Aedes; An., Anopheles; CHIKV, chikungunya virus; Cx., Culex; JE, Japanese encephalitis; LCEV, La Crosse encephalitis virus; MBD, mosquito-borne disease; SLEV, Saint Louis encephalitis virus; US, United States