Table 1.

Impacts of climatic variables as drivers in the epidemiology of WNV.

climatic variable	impacts on the epidemiology of WNV
temperature	correlates positively with:  —viral replication rates  —seasonal phenology of mosquito host populations  —growth rates of vector populations  —viral transmission efficiency to birds  —geographical variations in human case incidence correlates negatively with:  —interval between blood meals  —incubation time from infection to infectiousness in mosquitoes
precipitation (contradictory findings)	above average, floods	—leads to higher mosquito abundance—reduces potential by flushing drainage channels used by Culex larvae —correlates positively with potential for disease outbreaks in humans
	below average, drought	—facilitates population outbreaks of some mosquito species —‘rich’ standing water attracts several species of mosquitoes and birds; this increases the  bird–mosquito interaction and accelerates the epizootic cycling and amplification of WNV  within these populations
relative humidity	correlates positively with:  —vector population dynamics  —morbidity in humans
wind	contributes to virus spread by impact on wind-blown mosquitoes and on the arboviruses they transmit affects bird migration through changes in the patterns of storm tracks