August 16, 2007
West Nile Virus Update #9
A second human death related to a West Nile virus infection of a person in Manitoba in 2007 has been reported.
The person, a male in his 70s, was a resident of the Central Health Region and had contracted the more severe type of West Nile virus disease (West Nile virus neurological syndrome). Based on public health investigation to date, the man had other underlying medical conditions. The role that West Nile virus played in the death is under investigation.
The chief medical officer of health also advises that, as of noon today, 48 additional positive human test results for West Nile virus have been reported in Manitoba since last week.
To date, a total of 106 individuals have tested positive for West Nile virus (WNV) in Manitoba. Of these, 14 test results were identified by Canadian Blood Services routine screening and the donated blood units were discarded as planned.
Earlier this month, as reported previously on Aug. 4, a man in his 80s who tested positive for WNV died. It is likely West Nile virus was the cause of death.
Ongoing mosquito surveillance indicates that West Nile virus-infected mosquitoes continue to be present in all parts of southern Manitoba. To date, no evidence of West Nile virus-infected mosquitoes has been found in the NOR-MAN, Burntwood and Churchill health regions. The province continues to monitor adult Culex tarsalis mosquito numbers throughout Manitoba. The highest risk period of exposure to infected mosquitoes is expected to continue for the next few weeks.
No new orders under Manitoba’s Environment Act are being issued to control adult mosquitoes at this time. Adult mosquito control based on orders previously issued will continue in Deloraine and Winkler.
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 earlier in the day as well as between dusk and dawn. Manitobans are encouraged to reduce the risk of mosquito bites by:
· reducing the amount of time spent outdoors during peak mosquito hours between dusk and dawn or whenever mosquitoes are active;
· using appropriate mosquito repellent;
· wearing light-coloured, loose-fitting clothing; and
· maintaining door and window screens so they fit tightly and are free of holes.
The number of cases of the more severe type of West Nile virus (neurologic illness) in previous years has ranged from one to 35 cases per summer. The total number of cases of West Nile virus in previous years has ranged from three to 143. It is too early to know or to predict the number of severe cases that will be reported this year.
Additional information on human cases including age, gender, regional health authority of residence and likeliest area of exposure, as well as information on adult mosquito control schedules will be provided on the website as it becomes available at https://www.gov.mb.ca/health/wnv.
Health Canada has concluded the use of malathion for adult mosquito control in residential areas using ultra-low-volume application will not pose a health concern. However, people who wish to further reduce their exposure to malathion can take additional precautions including:
· closing all doors and windows,
· avoiding trucks while spraying is underway,
· turning off fans and air conditioners or setting them at exhaust,
· removing clothes and children’s toys from outdoor areas,
· rinsing any household items or toys left outside before using them, and
· washing fruits and vegetables.
Information on weekly average trap counts of Culex tarsalis by regional health authority and a list of communities where infected mosquitoes have been found is available on the province’s West Nile virus website at https://www.gov.mb.ca/health/wnv. Manitobans can check the West Nile virus website regularly for up-to-date data and information throughout the summer.
More information about West Nile virus is also available from Health Links–Info Santé at 788-8200 or 1‑888‑315-9257.
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