Table 3.

Vector control decision making process: recommended response for the different risk levels

Risk area 1	Risk level	Probability of human outbreak	Description	Recommended response
Predisposed	1	Unknown	Ecological condition suitable to WNV circulation AND past evidences of WNV circulation	Consider drafting WNV preparedness plan
Imperilled	2	Unknown	Ecological condition suitable to WNV circulation	Develop WNV preparedness plan, including surveillance activities and an integrated vector control plan
			AND past evidences of WNV circulation	Allocate resources necessary to enable emergency response
				Implement larval control as part of the integrated vector control in case of WNV circulation in previous year
Imperilled	3a	Low	Current surveillance findings (i.e. mosquito or birds screening) indicating WNV epizootic activity in the area, in the second part of the season (August-September-October)	As in risk level 2
				AND Implement public education programs focused on risk potential, personal protection, and emphasizing residential source reduction
				Vector control focuses on larval control
Imperilled	3b	Low to moderate	Current surveillance findings (i.e. mosquito or birds screening) indicating WNV epizootic activity in the area, in the first part of the season (May-June-July)	As in risk level 3a
				AND increase entomological and bird surveillance
				AND increase effort for public information on personal protection and continued source reduction
				AND If surveillance indicates virus circulation is increasing initiate ground adult control in areas at high risk for humans or in hot spot sites (if known)
Imperilled	4	High	WNV specific IgM detected in local non vaccinated horse(s) or WNV isolated from local horse.	As in risk level 3b
				If surveillance indicates virus circulation is increasing initiate ground adult control in areas at high risk for humans or in hot spot sites (if known)
Affected	5	ongoing outbreak, uncertainty about size	at least one human case detected (i.e. probable or confirmed human case according to EU case definition)	Response as in level 4
				AND intensify ground adult mosquito control with multiple applications in areas of high risk of human cases
				AND enhance risk communication
				AND monitor efficacy of spraying on target mosquito populations
				AND in case a large area is involved coordinate the program by an emergency unit with all authorities involved

¹Nomenclature according to [106].