With the first human cases of West Nile
virus disease for 2008 confirmed in three Minnesota residents,
state health officials today urged Minnesotans to protect themselves
from mosquitoes from now through September.

The first three
cases of the year are residents of Becker, Carver, and Clay counties.
The Clay County resident is a man in his 60s and the Becker and
Carver county individuals are both under the age of 20. They all
experienced onset of symptoms in early to mid-July and were later
diagnosed with West Nile fever, a milder form of WNV-related illness.
All three people are now recovering.

To limit further cases of this potentially life-threatening illness,
Minnesota Department of Health officials today strongly urged
people to use one of the many mosquito repellent options now available
and to take other simple precautions against mosquito bites this
season.

“Culex tarsalis,
the primary mosquito carrier of West Nile virus in Minnesota, was at
low levels earlier this summer when weather was cooler than normal, but
its numbers have begun to rise with recent warm weather,” said David
Neitzel, an MDH epidemiologist specializing in diseases carried by
mosquitoes and ticks. “Rising numbers of this mosquito species, the
first human cases, and recent findings from mosquito and bird
monitoring mean that the peak West Nile virus risk season has begun.”

Illness from West Nile virus can occur in residents throughout
Minnesota and among all age groups. However, risk is greatest in
western and central counties, where Culex tarsalis
mosquitoes are most common. Also, people who are elderly or who have
weakened immune systems face the highest risk of developing severe
illness from an infection. “They need to be especially diligent
about protecting themselves from mosquitoes,” Neitzel said.

Mosquito repellent provides an important first line of defense against mosquito bites.
Several safe and effective options are now available:

• Repellents
  containing DEET (up to 30 percent concentration) are still the most
  widely used and can provide long-lasting protection against mosquito
  bites.
• For people who prefer not to use DEET, effective
  alternatives include repellents containing picaridin, oil of lemon
  eucalyptus, or IR3535.
• Repellents containing
  permethrin are recommended for use on clothing (not skin). Permethrin
  is a strong repellent and will kill mosquitoes that come into contact
  with treated clothing.
• For maximum effectiveness and safety, all mosquito repellents should be used according to label directions.

“The key to avoiding WNV illness is to keep repellent on hand from
July through September, and to use it diligently,” Neitzel said.

Other important steps to prevent mosquito bites and serious illness from WNV include:

• Minimize outdoor activities at dusk and dawn, as this is
  prime feeding time for WNV-carrying mosquitoes. If you go outside at
  these times, take precautions even if mosquito numbers seem low; it
  only takes one bite from an infected mosquito to transmit the virus.
• Wear loose-fitting long-sleeve shirts and long pants if you must spend time in an area where mosquitoes are biting.

Culex tarsalis mosquitoes, which carry West Nile virus, prefer
agricultural areas of central and western Minnesota. While the majority
of Minnesota’s West Nile disease has occurred in people from these
areas, cases are possible anywhere within the state. Since WNV was
first found in Minnesota in 2002, 441 cases (including 14 fatalities)
of West Nile disease have been reported to MDH. Of those, 101 occurred
in 2007.

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

Symptoms usually show up three to 15 days after being bitten. They can
include headache, high fever, rash, muscle weakness, stiff neck,
disorientation, convulsions, paralysis and coma. Severe cases tend to
occur most often in the elderly and people with immune system problems.

Information on WNV can be found at the MDH web site: www.health.state.mn.us. Further information on repellents is at the CDC web site: www.cdc.gov/ncidod/dvbid/westnile/RepellentUpdates.htm.

People who have questions about West Nile virus can call MDH at
(651) 201-5414 or (877) 676-5414 between 8 a.m. and 4:30 p.m.
Monday through Friday.