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

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