EEE Decision Making - 2012 July 26, 2012

Timeline of Events First EEE mosquitoes, mammal-biting, Carver Meeting to discuss data and possible responses, including aerial spray EEE positives from Rehoboth, bird and mammal-biter First EEE mosquitoes, bird and mammal-biting, Easton, Raynham and Taunton moved to high risk Additional positives from Easton and Lakeville First EEE mosquitoes, bird-biting, Lakeville Aerial spray July 11 July 12 July 13 July 16 July 17 July 18 July 20-22 Decision to aerial spray made Additional trapping and testing throughout area

Comparison of First EEE Result Dates by Year

Historic Indicators applicability to 2012 Above average rainfall in prior fall and spring NO Mild winter with insulating snow cover YES EEE activity in the previous year YES Isolation of EEE virus from a mammal-biting mosquito species YES Infection of a human prior to late August NO Higher than average summer temperatures YES

C. melanura Mosquito Populations C. melanura (bird-biting mosquito) is about average right now in 2012. Peaks in the population have been associated with occurrence of human infections. 2011 was an example of this.

EEE Infection Rate in C. melanura MIR provides a measure of the proportion of infected mosquitoes in the population. Peaks in MIR have been associated with occurrence of human infections.

AIF Comparison 2010-2012 Multiplying mosquito population numbers by the infection rate creates a new risk indicator called the Abundance Infection Factor, AIF, which provides a measure of the density of the infected mosquito population. The Expert Panel recommended evaluation of this as a new tool for risk assessment.

Criteria for Inclusion in Spray Current EEE isolations Known breeding habitat Areas of historic risk

Bristol County Activity Proportion of C. perturbans (mammal-biting) infected in Bristol County traps only, comparison with 2010 and 2011 MIR in week 29 = 13.1

Approximate Locations of Positive Mosquito Traps with ~5 mile radius for Initial Discussion Purposes ONLY 10

Comparison of current activity zone (red) and 2006 and 2010 spray zones 2012 2010 2006b 2006a

Recent EEE Virus Activity in Plymouth and Bristol Counties: 2004-2012 Color codes: Gray indicates human or horse case Yellow indicates EEEv(+) mammal biting mosquitoes

Final Area Spray Zone Map Including Areas of Historic Risk

Public Risk Communication Areas at High Risk have all reported cooperating with advice to reschedule evening, outdoor events MCPs are continuing ground-spraying Personal prevention messages being stressed in releases