Editing IPCC:AR6/WGII/Chapter-14 (section)

==== 14.5.6.4 Vector-Borne Disease ====

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Climate change creates conditions that enable earlier seasonal activity and general northern expansion of ticks ( [[#Ogden--2014|Ogden et al., 2014]] ), increasing human exposure to tick-borne diseases in North America ( ''very high confidence'' ). Lyme disease incidence and geographic extent has already increased in Canada and the USA ( [[#Eisen--2016|Eisen et al., 2016]] ), which has been associated with climate change ( [[#Ogden--2014|Ogden et al., 2014]] ), including warmer temperatures ( [[#Cheng--2017|Cheng et al., 2017]] ; [[#Lin--2019|Lin et al., 2019]] ). Climate change is projected to increase disease spread into new geographic regions, lengthen the season of disease transmission and increase tick-borne disease risk in North America across emissions scenarios throughout this century ( ''very high confidence'' ), with regional variability ( [[#Roy-Dufresne--2013|Roy-Dufresne et al., 2013]] ; [[#Feria-Arroyo--2014|Feria-Arroyo et al., 2014]] ; [[#Monaghan--2015|Monaghan et al., 2015]] ; [[#Robinson--2015|Robinson et al., 2015]] ; [[#McPherson--2017|McPherson et al., 2017]] ). Chagas disease is transmitted by triatomines, and most of the Mexican population (88.9%) already reside in areas with at least one infected vector species in both rural and urban populations ( [[#Carmona-Castro--2018|Carmona-Castro et al., 2018]] ). Chagas has already extended its range into the southern USA, and the triatomines’ niche is projected to expand northward this century ( [[#Garza--2014|Garza et al., 2014]] ; [[#Carmona-Castro--2018|Carmona-Castro et al., 2018]] ) in both rural and urban areas ( [[#Carmona-Castro--2018|Carmona-Castro et al., 2018]] ).

Climate change is projected to impact the distribution, abundance and infection rates of mosquitoes in North America ( ''high confidence'' ), which will increase risk of mosquito-borne diseases including West Nile virus, chikungunya and dengue ( ''medium confidence'' ). The geographic distribution of West Nile virus is projected to expand in North America this century (A1B) ( [[#Harrigan--2014|Harrigan et al., 2014]] ). In the USA and Canada, mosquitoes are projected to emerge earlier in the year and remain active longer into the fall; however, mosquito population dynamics vary by location with northern locations projected to have an increased vector abundance, and currently hot areas may become ''too'' hot, thus negatively affecting mosquito survival (A2, A1B, B1) ( [[#Chen--2013|Chen et al., 2013]] ; [[#Morin--2013|Morin and Comrie, 2013]] ; [[#Brown--2015a|Brown et al., 2015a]] ).

Local transmission of chikungunya virus has emerged in Mexico and the USA since AR5, and areas suitable for transmission are projected to expand (RCP4.5 and RCP8.5) ( [[#Tjaden--2017|Tjaden et al., 2017]] ). Although chikungunya virus is not currently in Canada, climate change is projected to make southern British Columbia suitable for virus transmission this century, particularly under RCP8.5 ( [[#Ng--2017|Ng et al., 2017]] ).

The dengue mosquito vector is well established in Mexico and the southeast USA. In northwest Mexico, incidence of dengue cases is associated with minimum monthly temperature ( [[#Diaz-Castro--2017|Diaz-Castro et al., 2017]] ), and the geographic range of the vector in the USA is restricted, in part, by low temperatures. Thus, a northward range expansion is projected; however, future dengue risk also depends on built environments and competition with other mosquito species ( [[#Colón-González--2013a|Colón-González et al., 2013a]] ; [[#Eisen--2013|Eisen and Moore, 2013]] ). Climate change is projected to increase the geographic range and extend the seasonal activity of the dengue vector in the southern USA by 2045–2065 (A1B); however, transmission is projected to be limited by low winter temperatures in the mainland USA, potentially preventing its permanent establishment ( [[#Butterworth--2017|Butterworth et al., 2017]] ). In Mexico, increased dengue cases are projected this century (A1B, A2, B1) ( [[#Colón-González--2013b|Colón-González et al., 2013b]] ).

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