MANITOBA HEALTH, HEALTHY LIVING & SENIORS WEEKLY WEST NILE VIRUS SURVEILLANCE REPORT (WEEK 27)

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1 MANITOBA HEALTH, HEALTHY LIVING & SENIORS WEEKLY WEST NILE VIRUS SURVEILLANCE REPORT (WEEK 27) The weekly West Nile Virus Surveillance Reprt utlines the mst current surveillance data and is psted weekly n the website ( during the summer seasn. Surveillance data are subject t change and will be updated accrdingly as new infrmatin becmes available. Manitba Health, Healthy Living & Senirs (MHHLS) cnducts surveillance fr West Nile virus (WNV) within human, msquit & hrse ppulatins annually: Msquit: Msquit surveillance is cnducted twice per week between mid-may and mid-september (weather dependent) in a number f suthern Manitba cmmunities. In Manitba WNV testing is cnducted n Culex tarsalis msquites, the principal vectrs f WNV, and bth msquit numbers and infectin rates (i.e. psitive msquit pls*) are reprted. Cmmunities chsen fr msquit trap placement were selected based n ppulatin density, lcal evidence f prir WNV activity and representative gegraphic distributin. Human: Human WNV surveillance is cnducted thrughut the year (January December) by Cadham Prvincial Labratry and Canadian Bld Services, with all data reprtable t MHHLS. Human cases are included in the Weekly WNV Surveillance Reprt based n the date they are reprted t MHHLS. Case classificatin infrmatin is nt included in this reprt. Hrse: Surveillance f WNV in hrses is cnducted by Manitba Agriculture Fd and Rural Develpment (MAFRD) with cases reprted t MHHLS as detected. The risk f WNV transmissin is expected t be present thrughut suthern Manitba each year and msquit trapping prvides a lcalized estimate f WNV risk. The absence f traps in a cmmunity r regin des nt imply that there is n risk f WNV in thse lcatins. Further, lw Culex tarsalis numbers and/ r infectin rates shuld nt be interpreted as zer risk. Residents and visitrs are strngly encuraged t prtect themselves frm msquit bites thrughut the seasn even in areas with n msquit traps r lw WNV activity. The accumulatin f Degree Days* are recrded thrughut the seasn as there is a general crrelatin between increased and/ r rapid accumulatin f Degree Days and WNV transmissin risk. Warmer temperatures assciated with increased Degree Days serve t decrease msquit develpment times, shrten the WNV incubatin perid and increase biting activity. All f which can increase the risk f WNV transmissin, shuld ther cnditins als be favurable. Seasnally the greatest accumulatin f Degree Days typically ccurs in the suthwestern prtin f the prvince and alng the Red River valley. Fr additinal West Nile virus infrmatin, including precautinary measures and symptms, please cnsult the MHHLS WNV website ( r cntact Health Links at (in Winnipeg) r tll free at * Fr a mre detailed descriptin ff msquit pl & degree days cnsult Appendix 2. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 1

2 - WNV Prvincial Surveillance Data - T date (as f Week 27*) there has been n WNV activity detected in Manitba (Figure 1). In Week 27 (June 29 July 5) Culex tarsalis msquites were cllected frm twenty-ne (21) sentinel cmmunities spread acrss all fur suthern Manitba Health regins; Interlake-Eastern, Prairie Muntain, Suthern and Winnipeg (Table 1 & 2; Figure 2). Nte that the rainy and windy weather experienced ver the Canada Day lng weekend interfered with regular trapping peratins in a number f cmmunities. * Fr a listing f CDC surveillance weeks and crrespnding dates fr the 214 please see Appendix Year-End WNV Surveillance Data* In 213 a ttal f 3 human WNV cases were reprted t Manitba Health, Healthy Living & Senirs frm three suthern Manitba Health Regins (Interlake-Eastern, Suthern and Winnipeg). Tw (2) f the WNV human cases were classified as the less severe nn-neurlgical syndrme, while ne was classified as the mre severe neurlgical syndrme. The individual with the WN Neurlgical Syndrme passed away frm their symptms, marking the first lcal fatality attributed t WNV since 28. In 213 a ttal f 19 WNV psitive msquit pls were cllected frm 1 cmmunities acrss three suthern Manitba Health Regins (Prairie-Muntain, Suthern and Winnipeg). In 213 three WNV psitive hrses were reprted, tw frm the Suthern Health Regin and ne frm the Prairie Muntain Health Regin. A ttal f tw WNV psitive birds were reprted, ne frm the Prairie Muntain Health Regin and the ther frm the Winnipeg Health Regin. * This summary sectin will be remved upn the detectin f WNV activity in Manitba. Table 1 Average number f Culex tarsalis msquites captured by Health Regin (current t Week 27) Health Regin CDC Week Interlake- Eastern Prairie Muntain Suthern Winnipeg Prvincial Average Indicates that ne r mre psitive msquit pls were detected within the health regin. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 2

3 Figure 1 WNV activity by Health Regin within Manitba (current t Week 27). Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 3

4 Table 2 Average number f Culex tarsalis msquites cllected by surveillance cmmunity in suthern Manitba three week trend (current t Week 27). Health Regin Cmmunity Week 27 Week 26 Week 25 Interlake- Eastern Prairie Muntain Suthern Winnipeg Beausejur Gimli Oakbank Selkirk Stnewall Bissevain Brandn Carberry.33.. Dauphin... Killarney Minnedsa... Siux Valley FN Suris Virden Altna Carman Headingley Mrden Mrris Niverville Prtage la Prairie Rseau River FN Ste. Anne Sandy Bay FN Steinbach. 1.. Winkler East St Paul West St Paul Winnipeg * Tp three cmmunities with the highest weekly average f Culex tarsalis are indicated in bld. ** Adult msquit trapping started during CDC Week 21. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 4

5 Figure 2 Average number f Culex tarsalis msquites cllected acrss suthern Manitba during Week 27. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 5

6 Surce: Map prduced curtesy f Agriculture and Agri-Fd Canada. Figure 3 - Degree day accumulatins, as f Week 27, acrss the Prairie Prvinces. Table 3 Ttal number f human WNV cases*, by Health Regin f residence, reprted t Manitba Health, Healthy Living & Senirs by labratries (current t Week 27) Health Regin CDC Week Interlake- Eastern Prairie Muntain Suthern Winnipeg Ttals Ttals * Nte that cases are presented by week reprted t MHHLS, adjustments may be made as mre details (such as expsure CDC week) becme available thrugh fllw-up investigatin. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 6

7 Table 4 Ttal number f Culex tarsalis msquit pls tested during the 214 seasn by health regin (current t Week 27) Health Regin Interlake- Eastern Prairie Muntain CDC Week Ttals Suthern Winnipeg Weekly Ttals Table 5* Ttal number and percentage f WNV psitive Culex tarsalis msquit pls by Health Regin (current t Week 27) Health Regin Interlake- Eastern Prairie Muntain CDC Week () () Suthern () Winnipeg () Weekly Ttals () () () () () () () () () () () () () () () () () () () () () () () () () () Ttals () () () () () () () () () () * Nte that numbers utside brackets represent psitive pls, numbers within represent the percentage f ttal pls that tested psitive fr WNV. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 7

8 Table 6 Cmparisn f year-t-date cumulative and year-end ttal West Nile virus in Manitba (current t Week 27) Year Cumulative (Year-t-Date) Amunt Psitive Msquit Pls Human WNV Cases Psitive Msquit Pls Year End Ttals Human WNV Cases 214 TBD TBD Canada: - WNV Activity in Canada and the U.S. - As f Week 27 there has been n WNV activity reprted in Canada (Table 7). Additinal up t date Canadian WNV infrmatin can be btained by cnsulting the Public Health Agency f Canada West Nile virus website at United States: As f Week 27 a ttal f eighteen (18) human WNV cases, including ne (1) death, have been reprted in the United States. In additin 256 WNV psitive msquit pls, 22 WNV psitive birds and 1 WNV psitive hrse have been identified acrss the United States. As f Week 27 Minnesta is reprting tw (2) WNV psitive msquit pls (Table 7). As f Week 27 Nrth Dakta is nt reprting any WNV activity (human, msquit, bird r hrse). As f Week 27 Suth Dakta is reprting three (3) human WNV cases, and ne (1) WNV psitive msquit pl (Table 7). Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 8

9 Additinal up t date U.S. WNV infrmatin can be btained by visiting the United States Gelgical Survey s Arbnet Website at Table 7 Psitive human, msquit, hrse and bird West Nile Virus surveillance indicatrs acrss Canada and neighburing US states as f Week 27. Prvince/ State Human Cases* Psitive Msquit Pls Veterinary *** Birds Manitba Saskatchewan Alberta N/A** N/A Nrth Dakta N/A Suth Dakta 3 1 Minnesta 2 Ontari British Clumbia Quebec Maritimes N/A N/A TOTAL 3 3 * Table numbers include travel related cases. ** Jurisdictins with N/A (nt applicable) d nt maintain regular surveillance. *** Veterinary cases are primarily, but nt all, hrse cases. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 9

10 CDC Week Number - APPENDIX 1 - Table CDC surveillance weeks Dates CDC Week Number Dates 21 May 18 - May 24 3 July 2 - July May 25 May July 27 - August 2 23 June 1 - June 7 32 August 3 - August 9 24 June 8 - June August 1 - August June 15 - June August 17 - August June 22 - June August 24 - August 3 27 June 29 - July 5 36 August 31 - September 6 28 July 6 - July September 7 - September July 13 - July September 14 - September 2 - Appendix 2 - Average number f Culex tarsalis This weekly value prvides an estimate f the Culex tarsalis numbers and activity. The ptential risk f WNV transmissin is greater when mre Culex tarsalis are present shuld the virus itself be present and ther cnditins prve favrable. It is calculated by dividing the ttal number f Culex tarsalis msquites captured in the specified area by the ttal number f trap nights fr the week (a trap night is recrded fr each night that a trap was peratinal). EXAMPLE: 12 Culex tarsalis cllected; 2 traps perating n 2 nights (= 4 trap nights); Average number = 12 (Culex tarsalis)/ 4 trap nights = 3. Degree Day Degree days are a measurement f heat accumulatin. The threshld temperature belw which West Nile virus develpment des nt ccur (when in msquites) is 14.3 C. Degree days are calculated by taking the daily mean temperature and subtracting the cut-ff threshld: EXAMPLE: Mean Temperature = 19.3 C; Degree Day threshld = 14.3 C; = 5. Degree Days. During the seasn a running ttal f accumulated Degree Days is recrded. It is generally assumed that a ttal f 19 Degree Days are required fr virus develpment t be cmpleted and ptential transmissin t ccur. The risk f transmissin increases with increasing Degree Day accumulatin. Mrever, cnsistently warmer temperatures will significantly shrten virus develpment time thereby increasing the ptential risk f WNV transmissin shuld the virus itself be present and ther cnditins prve t be favrable. Msquit Pl Msquites f the same species, cllected frm the same trap n the same date are pled tgether fr the purpses f labratry testing. Culex tarsalis msquites cllected frm ne trap n a given night are placed in pls f 1 5 msquites fr WNV testing. When mre than 5 Culex tarsalis msquites are cllected frm the same trap multiple pls are tested. Thus a psitive pl refers t the detectin f WNV in between 1 5 Culex tarsalis msquites cllected frm a given trap. Manitba Health, Healthy Living & Senirs Weekly WNV Surveillance Reprt (WEEK 27) Page 1