During the summer months, mosquitoes are regularly monitored at sites around the state for mosquito-borne diseases. Each week, mosquitoes are collected at various locations by the Vermont Agency of Agriculture. These collections of mosquitoes are tested for arborviruses - mosquito-borne viruses - that may affect Vermonters: West Nile Virus and Eastern Equine Encephalitis. The Health Department summarizes mosquito testing results and reports of human and animal illnesses every week during the summer and early fall, and compiles data each year in an annual surveillance report.

Check out the Mosquito Surveillance Map


2024 Surveillance for Viruses Spread by Mosquitoes

a chart depicting the 2024 % positivity rate for West Nile and Eastern Equine Encephalitis positive mosquito pools, compared to historic averages and historic high's for both pathogens.
What does this graph tell me?
  • Lines represent historic (2002–2023) average percentage of mosquito pools positive for WNV (solid line) and EEE (dotted line).
  • Bars show the percentage of mosquito pools positive in the current year.
  • Historically, the percentage of mosquito pools positive for an arbovirus increases in late August and peaks in mid-September.

Mosquito Surveillance Results

Collection week# of Mosquito Pools* Tested# of EEEV Positive Pools# of WNV Positive Pools
June 9-152600
June 16-222300
June 23-2917200
June 30-July 617200
July 7-1317201 (Alburgh)
July 14-2017202 (Vergennes, Hardwick)
July 21-271723 (Alburgh, Swanton)3 (Alburgh, Vergennes, St. Albans City)
July 28-August 33187 (Alburgh, Colchester)13 (Bradford, Newport City, Hardwick, Whiting, Essex Junction, St. Albans City, Alburgh)
August 4-1027711 (Alburgh, Highgate, Cornwall, Whiting, Milton, Colchester, Sudbury, Swanton)10 (Alburgh, Highgate, Vergennes, Grand Isle, Essex Junction, St. Albans City)
August 11-1734426 (Alburgh, Colchester, Fairfield, Grand Isle, Milton, Swanton, Vergennes, Whiting)9 (Alburgh, Derby, Essex Junction, Grand Isle, Hardwick, Montpelier)
August 18-2435419 (Benson, Brandon, Cornwall, Leicester, New Haven, Sudbury, Whiting, Alburgh, Grand Isle, Colchester)5 (Essex Junction, St. Albans City, Grand Isle, Springfield, Rockingham)
August 25-315059 (Whiting, New Haven, Colchester, Alburgh, Swanton)10 (Stowe, Rockingham, Montpelier, Alburgh, Essex Junction, Burlington)
September  1-74843 (New Haven, Whiting, Milton)3 (Vergennes, Newport City, Bennington)
September 8-1434400
September 15-213284 (Leicester, Benson, Whiting)7 (Leicester, Milton, St. Albans City, Essex Junction, Swanton, Vergennes)
September 22-282612 (Grand Isle, Alburgh)0
September 29-October 51901 (Swanton)1 (Milton)
October 6 - 121431 (Morristown)0
October 13-193300
Year-to-date4,4908664

*A mosquito pool is a group of 1-50 mosquitoes of the same species, collected at the same trap location, on the same date.

Animal Surveillance

  • 1 animal case of EEE in Addison County (Salisbury) and 1 animal case of EEE in Orleans County (Charleston) have been reported in 2024. 
  • No animal cases of WNV has been reported in 2024.
     

Vermont veterinarians: Free EEE and WNV testing in animals is available. 

Human Surveillance

  • 1 human case of WNV in Chittenden County has been reported in 2024.
  • 2 human cases of EEE in Chittenden County have been reported in 2024. 

Aedes albopictus Surveillance

  • The Aedes albopictus (Asian tiger) mosquito can carry and transmit Zika, dengue, and other arboviruses. It has an estimated geographic range that includes southern Vermont.
  • After four consecutive years of detections at a single trap site in Windham County, spanning several weeks of detection each year, Aedes albopictus is considered established (locally-reproducing) at this location.

Annual Surveillance Reports

 

Topics:
Disease Reporting | Mosquito-borne Diseases
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