August 25, 2005
Since last week’s update on Aug. 18, there have been 14 additional positive test results for West Nile virus in Manitobans. This brings the total number of Manitobans that have tested positive for West Nile virus this year to 26.
Following investigation by public health officials, 16 cases have been determined to be probable cases of West Nile virus.
Six have been classified as probable cases of West Nile neurological syndrome. Five of these individuals were admitted to hospital. Two individuals remain in hospital.
Eight have been classified as probable cases of West Nile non-neurological syndrome. These individuals did not require hospitalization.
Two have been classified as probable asymptomatic cases of West Nile virus. These cases were identified by Canadian Blood Services. The individuals did not show symptoms.
No deaths have been reported. The remaining 10 cases are currently under investigation to determine their status. This includes one test result identified by Canadian Blood Services.
Of the 16 classified cases:
four are Winnipeg Regional Health Authority residents,
four are Assiniboine Regional Health Authority residents,
two are Interlake Regional Health Authority residents,
three are Central Regional Health Authority residents,
one is a Brandon Regional Health Authority resident,
one is a North Eastman Regional Health Authority resident, and
one is a South Eastman Regional Health Authority resident.
Based on investigation of these cases, exposure has occurred in all of the seven southern regional health authorities.
Further information on human cases will be posted on the website when it becomes available. So far this year, 1,329 people have been tested for WNV in Manitoba.
During the week of Aug. 14 to 20, average Culex tarsalis trap counts decreased significantly in all regional health authorities. Estimated infection rates in mosquitoes decreased or remained relatively unchanged from the previous week in most regions; however, they increased in the Assiniboine and Interlake regional health authorities. Since the last update, no new communities have had West Nile virus positive mosquito samples. Surveillance will continue to determine the potential risk of human exposure to West Nile virus.
Although mosquito counts have decreased, there are still infected mosquitoes in southern Manitoba. For the remainder of August and early September, the importance of taking personal protective precautions against mosquitoes continues. As daytime and evening temperatures become cooler, Culex tarsalis mosquitoes may become more active during the day as well as between dusk and dawn.
Manitobans can reduce the risk of mosquito bites by:
checking that door and window screens fit tightly and are free of holes;
reducing the amount of time spent outdoors whenever mosquitoes are active;
wearing light-coloured, loose-fitting clothing; and
using appropriate mosquito repellent.
Based on weekly mosquito surveillance data, adult mosquito control under a ministerial order continues to be on hold in Winnipeg, Winkler, Carman, the R.M. of West St. Paul and the R.M. of East St. Paul. While current data indicates a lower risk to human health, the risk may still rise. For this reason, the ministerial orders are still in place, even though there are no immediate plans for fogging at this time.
Birds from the NOR-MAN Regional Health Authority, the Burntwood Regional Health Authority and the Churchill Regional Health Authority will continue to be tested for WNV to establish the presence of WNV in those areas. No further birds are required for testing from southern Manitoba.
Public information about West Nile virus and mosquito control in areas under a health order is available by calling Health Links-Info Santé at 788-8200 in Winnipeg or toll-free at 1-888-315-9257. Information is also available on the Manitoba Health website at http://www.gov.mb.ca/health/wnv.
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