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Table 3 Vector control decision making process: recommended response for the different risk levels

From: A review of the vector management methods to prevent and control outbreaks of West Nile virus infection and the challenge for Europe

Risk area1 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
  1. 1Nomenclature according to [106].