Twenty-Nine Cases of West Nile Virus Confirmed in Minnesota

Update: There are 29 confirmed cases of West Nile virus in Minnesota as of Thursday, Aug. 29.

Two deaths are included in that total.

None of the West Nile cases are in Dakota, but there have been two cases reported in Ramsey County, one in Hennepin County and one in Scott County.

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Original post, Aug. 13: The Minnesota Department of Health has attributed the season’s first death to West Nile Virus, a disease transmitted by mosquitoes. A man in Murray County died late last week, officials reported.

It’s the first death of 2013, matching last year’s total number of deaths attributed to the virus. In 2012, 70 cases of West Nile were reported. That number has hit 16 so far this season, but is expected to rise this month after a boom in the mosquito population around the Fourth of July weekend.

Last year at this time, for example, there were less than a dozen cases reported.

Toward the end of June and early July, the Metropolitan Mosquito Control District reported the Twin Cities area experienced a “double hatch,” meaning the cooler, wet portion of June delayed the first hatch of mosquito eggs, while the second was right on time, making them happen almost simultaneously.

The mosquito population has decreased since then, thanks to drier conditions in July. An extended period of dry weather –which we’re in the middle of right now–will only help continue to slow the spread of West Nile, the MDH stated. However, WNV is reaching its peak season.

David Neitzel, an MDH epidemiologist specializing in diseases carried by mosquitoes, said that will continue through early autumn.

"The species of mosquito that transmits the virus to humans is most abundant in July and August. Mosquito repellents used during outdoor activities at dusk and dawn can prevent this potentially severe disease,” he added.

About 1 out of 150 people bitten by a WNV-infected mosquito will develop central nervous system disease (encephalitis or meningitis). Approximately 10 percent of people with this severe form of infection die from their illness, and survivors can suffer from long-term nervous system problems. Fortunately, most people bitten by infected mosquitoes develop West Nile fever, the less severe form of disease, or fight off the virus without any symptoms.

One way the Department of Health uses to track West Nile is by monitoring donations at local blood banks and blood drives. Last year 33 cases in 20 different counties were found through typing and testing. This year, two of the 16 reported cases have been found through this system.

Prevention

According to the MDH: The number of mosquitoes that are actually capable of causing infection in humans is relatively small, but it is always advisable to take preventive measures to protect yourself.

• Wear mosquito repellent containing up to 30% DEET (10% for children).
• Wear long sleeve shirts and pants.
• Avoid outdoor activity at peak mosquito feeding times (dawn and dusk).
• Eliminate water-holding containers (buckets, tires, etc.) from your property.
  This will reduce numbers of several mosquito species.

• Spray Before You Work or Play West Nile Virus Prevention Poster