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Incidence of West Nile Virus and other Mosquito Borne Viruses in Virginia in 2003

Incidence of West Nile Virus and other Mosquito Borne Viruses in Virginia in 2003. 1. Humans:. 29 cases. 24 cases. (2 deaths). (1 death). 2. Birds:. 932. 1,041. 3. Sentinel Chickens:. 6 flocks. 21 flocks. 10 birds. 54 birds. 4. Horses:. 48. 234. 5. Mosquito Pools:. 223.

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Incidence of West Nile Virus and other Mosquito Borne Viruses in Virginia in 2003

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  1. Incidence of West Nile Virus and other Mosquito Borne Viruses in Virginia in 2003

  2. 1. Humans: 29 cases 24 cases (2 deaths) (1 death) 2. Birds: 932 1,041 3. Sentinel Chickens: 6 flocks 21 flocks 10 birds 54 birds 4. Horses: 48 234 5. Mosquito Pools: 223 432 Virginia WNV Positive Totals, 2002 and 2003: 2002 2003 1.

  3. Human WNV Cases (29 total cases as of Dec. 31, 2002) Spatial and temporal distribution of WNV positive birds in Virginia in 2002; mid-August cut off date between early and late birds. . WNV Positive Birds as of Dec. 31, 2002 WNV Positive Birds (before 8/18/02) WNV Positive Birds (after 8/17/02) 2.

  4. WNV Positive Birds as of Dec. 31, 2003 WNV Positive Birds (before 8/2/03) WNV Positive Birds (after 8/1/03) Spatial and temporal distribution of WNV positive birds in Virginia in 2003; early-August cut-off date between early and late birds. 3.

  5. WNV Positive Birds as of Dec. 31, 2003 WNV Positive Birds (before 8/2/03) WNV Positive Birds (after 8/1/03) Spatial and temporal distribution of WNV positive birds in Virginia in 2003; early-August cut off date between early and late birds. Human WNV Cases (24 total cases as of Dec. 31, 2003) 4.

  6. WNV Positive Birds as of Dec. 31, 2003 WNV Positive Birds (before 8/2/03) WNV Positive Birds (after 8/1/03) Spatial and temporal distribution of WNV positive birds in Virginia in 2003; early-August cut off date between early and late birds. WNV Infected Horses (234 total as of Dec. 31, 2003) 5.

  7. WNV Positive Mosquitoes (Pools) in VA. 432 Number of Mosquitoes Tested for WNV Loudoun Co. 1 to 99 12 Charlottesville/ Albemarle Co. Fairfax Co./Fairfax 100 to 499 26 Alexandria Arlington Co. 105 500 to 1,999 31 Richmond 151 2,000 to 9,999 Henrico Co. 4 Hopewell 10,000 to 49,999 11 >50,000 Botetourt Co. 1 8 1 Hampton 2 12 Virginia Beach. 11 Norfolk 4 Chesapeake 11 14 Portsmouth Petersburg 18 Roanoke 6 Chesterfield Co. 5 Roanoke Co. Suffolk WNV Mosquito Surveillance Efforts, by Jurisdiction, in Virginia in 2003; WNV Positive Mosquitoes found 6.

  8. NUMBER TESTED SPECIES 69,681 Cq. perturbans 65,939 Ps. columbiae POSITIVE POOLS NUMBER TESTED POSITIVE POOLS 37,464 Oc. infirmatus SPECIES Oc. trivittatus 36,211 Cs. melanura 20 845 0 34278 Oc. sticticus Cx. salinarius 21 28,642 814 Oc. japonicus 0 Oc. canadensis 25,214 Ur. sapphirina 0 780 0 10,757 Cx. spp. Cx. pipiens 285 383 0 7,922 Unidentified Mosquitoes An. crucians 0 301 0 4,488 An. spp. Ae. vexans 2 21 0 4,355 Ae. spp Cx. restuans 72 14 0 4,320 TOTAL Ae. albopictus 4 2,578 18 5,099 2,303 Oc. sollicitans 0 1,232 0 2,136 An. crucians/bradleyi 388 0 0 2,124 Cx. erraticus 1 0 368 1,610 Oc. taeniorhynchus 0 1,038 432 351,405 Ps. ferox 0 Oc. atlanticus/tormentor 0 An. quadrimaculatus 0 An. punctipennis 0 Oc. triseriatus 0 Cx. pipiens/restuans 9 A Total of 351,405 Mosquitoes were Tested for WNV in 2003; 434 Pools Tested WNV Positive. 7.

  9. WNV Positive Mosquito Species in 2003: Number Tested per Positive Mosquito Species Positive Pools Mosquitoes Tested Culex pipiens 285 35,067 123 Culex restuans 72 20,364 282 Culex salinarius 21 59,545 2,835 Culiseta melanura 20 68,200 3,410 Culex spp. 18 4,353 241 Culex pipiens/restuans 9 757 84 Aedes albopictus 4 9,061 2,265 Aedes vexans 2 24,188 12,094 Culex erraticus 1 2,639 2,639 8.

  10. WNV Positive Birds (before 8/2/03) WNV Positive Birds (after 8/1/03) WNV Human Cases WNV Horse Cases LOUDOUN CO.. ARLINGTON CO.. ALEXANDRIA FAUQUIER CO.. FAIRFAX CO.. PRINCE WILLIAM CO.. CULPEPER CO.. WNV in Birds, Humans and Horses in Northern VA in 2003. 9.

  11. LOUDOUN CO.. ARLINGTON CO.. ALEXANDRIA FAUQUIER CO.. FAIRFAX CO.. PRINCE WILLIAM CO.. CULPEPER CO.. WNV in Birds, Humans and Horses in Northern VA in 2003. Data from dark gray jurisdictions is seen in following chart 10.

  12. 5000 4500 4000 Mosquitoes Tested 3500 All Culex spp. 3000 2500 2000 1500 1000 500 0 20 22 24 26 28 30 32 34 36 38 40 42 44 20 100 22 18 90 WNV Positives 16 80 Culex spp. 14 70 spp. (Pools) WNV Positive Birds 12 60 Humans Number of WNV Positives 10 50 8 Horses 40 6 30 4 20 Culex 2 10 0 0 44 20 22 24 26 28 30 32 34 36 38 40 42 WNV Activity in Northern VA (Alexandria, Arlington Co. , Fairfax Co., Loudoun Co. and Prince William Co.) During the 2003 Season. May June July Aug. Sept. Oct. spp. Tested Culex Week 11.

  13. WNV Positive Birds (before 8/2/03) MATHEWS CO. WNV Positive Birds (after 8/1/03) GLOUCESTER CO. WNV Human Cases WNV Horse Cases HAMPTON NORFOLK PORTSMOUTH ISLE OF WIGHT VA BEACH SUFFOLK CHESAPEAKE WNV in Birds, Humans and Horses in the Tidewater Region in 2003. 12.

  14. MATHEWS CO. GLOUCESTER CO. HAMPTON NORFOLK PORTSMOUTH ISLE OF WIGHT VA BEACH SUFFOLK CHESAPEAKE WNV in Birds, Humans and Horses in the Tidewater Region in 2003. Data from dark gray jurisdictions is seen in following chart 13.

  15. WNV Activity in the Tidewater Area (Hampton, Norfolk, Portsmouth., Chesapeake, Suffolk, Virginia Beach and Isle of Wight Co.) in 2003. May June July Aug. Sept. Oct. 8000 Mosquitoes Tested 7000 Culex pipiens 6000 Culiseta melanura 5000 4000 3000 2000 1000 0 5 32 50 37 26 WNV Positives WNV Positives 20 4 Birds 18 Cx. pipiens Humans 16 Cs. melanura 3 Horses 14 Number of WNV Positives 12 2 10 8 1 6 4 0 2 0 20 20 22 22 24 24 26 26 28 28 30 30 32 32 34 34 36 36 38 38 40 40 42 42 44 44 Mosquitoes Tested Mosquitoes (Pools) WNV Positive Week 14.

  16. WNV Positive Birds (before 8/2/03) CAROLINE CO. WNV Positive Birds (after 8/1/03) WNV Human Cases HANOVER CO. WNV Horse Cases KING AND QUEEN CO. KING WILLIAM CO. POWHATAN CO. NEW KENT CO. HENRICO CO. RICHMOND CHESTERFIELD CO. CHARLES CITY CO. AMELIA CO. PRINCE GEORGE CO. PETERSBURG WNV in Birds and Humans in the Richmond Area in 2003. 15.

  17. CAROLINE CO. LOUISA CO HANOVER CO. KING AND QUEEN CO. GOOCHLAND CO KING WILLIAM CO. POWHATAN CO. NEW KENT CO. HENRICO CO. RICHMOND CHESTERFIELD CO. CHARLES CITY CO. AMELIA CO. PRINCE GEORGE CO. PETERSBURG WNV in Birds and Humans in the Richmond Area in 2003. 16.

  18. May June July Aug. Sept. Oct. 1800 1600 Mosquitoes Tested 1400 Culex pipiens. 1200 Cx. pipiens Tested 1000 800 600 400 200 0 20 22 24 26 28 30 32 34 36 38 40 42 44 20 25 WNV Positives 18 16 Cx. pipiens 14 (Pools) WNV Positive Birds 12 Humans 10 Number of WNV Positives Horses 8 6 4 Cx. pipiens 2 0 20 22 24 26 28 30 32 34 36 38 40 42 44 Week 20 18 16 14 12 10 8 6 4 2 0 WNV in Birds and Humans in the Richmond Area (Richmond, Petersburg, Hopewell, Colonial Heights, Chesterfield Co., and Henrico Co in 2003. 17.

  19. EEE Positives 42 Mosquito Pools Horses 9 Sentinel Chickens Human Case 27 3 1 7 1 10 21 21 6 Eastern Equine Encephalitis in Mosquitoes, Horses, Sentinel Birds and Humans in Virginia in 2003. 18.

  20. EEE in Mosquitoes, Horses, Sentinel Birds and Humans in Virginia During 2003. Oct. May June July Aug. Sept. 6000 Mosquitoes Tested 5000 Culiseta melanura Culex salinarius 4000 3000 Mosquitoes Tested for EEE 2000 1000 0 20 22 24 26 28 30 32 34 36 38 40 42 44 9 9 EEE Positives EEE Positives 8 8 7 7 Chickens Cx. salinarius Cs. melanura Human 6 6 Horses 5 5 Mosquitoes (Pools) EEE Positive Number Testing EEE Positive 4 4 3 3 2 2 1 1 0 0 20 22 24 26 28 30 32 34 36 38 40 42 44 Week 19.

  21. LaCrosse Encephalitis 4 Human Cases Augusta Co. Tazwell Co LaCross Encephalitis (LAC) in Virginia in 2003. LAC Activity in Augusta County, VA is further east and north of where LAC cases have usually been found. 20.

  22. Conclusions: 1. WNV has not spread across Virginia as quickly as in other more northern states, but the 2003 season showed a dramatic increase in the distribution of WNV over its 2002 distribution 2. Although WNV may be found over large areas of the state, its activity appears to be focal or clustered (localized) in most areas. 3. Urban areas appear to have more intense WNV activity, partly because there are more people to report dead birds, or become sick themselves, but also because urban storm sewer systems and an abundance of containers provide a good breeding ground for Culex pipiens. 21.

  23. Conclusions: 4. The early occurrence of WNV infected birds in the 2002 and 2003 seasons indicated localities where there was greater potential for occurrence of human cases. 5. In 2002 and 2003, human cases were more likely to live near where early clusters of WNV infected birds occurred. 6. Human cases rarely occurred where no early birds had been found, but there were many areas where heavy, early WNV activity was seen in birds, but no local human cases occurred. 22.

  24. Conclusions: 7. WNV infected birds are good early indicators of WNV activity, but good mosquito surveillance can also provide a good early warning system. 8. In areas where human cases occurred, bird surveillance indicated WNV activity from 6 to 9 weeks before the first human case and mosquito surveillance indicated WNV activity from 2 to 7 weeks in advance. 9. Human cases typically occurred during, or just after the first big peak (increase) in the number of infected Cx. pipiens. 23.

  25. Conclusions: 10. Culiseta melanura mosquitoes may serve as a good indicator for WNV activity, but Cx. pipiens are a much more sensitive species to monitor because very few have to be tested to yield WNV positives 11. The use of properly baited gravid traps to detect Culex pipiens mosquitoes is the most effective method of mosquito surveillance for WNV. 12. WNV infection in horses indicates local WNV activity, but horses do not serve as good sentinels because they usually get WNV at the same time or later in the season than most humans do. 24.

  26. The End

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