Minnesota records first death from tick-borne Powassan virus

State health officials emphasize the importance of
preventing tick bites

A woman in her 60s from northern Minnesota has died from a brain
infection due to Powassan (POW) virus. This is the first death in
the state attributed to the disease. One other likely POW case has
been identified this year in Minnesota, in an Anoka County man in
his 60s who was hospitalized with a brain infection and is now
recovering at home. POW virus is transmitted through the bite of an
infected tick.

Both 2011 cases became ill in May after spending time outdoors
and noticing tick bites. The fatal case was likely exposed to ticks
near her home. The case from Anoka County might have been exposed
near his home or at a cabin in northern Minnesota.

Health officials say this death serves as a reminder of the
vital importance of preventing tick bites. “Although Powassan cases
are rarely identified, it is a severe disease which is fatal in
about 10 percent of cases nationwide, and survivors may have
long-term neurological problems” said Dr. Ruth Lynfield, state
epidemiologist with the Minnesota Department of Health (MDH).

“Powassan disease is caused by a virus and is not treatable with
antibiotics, so preventing tick bites is crucial.”

In Minnesota, POW virus can be transmitted by the blacklegged
tick (also called the deer tick), which can also carry Lyme
disease, anaplasmosis, and babesiosis. The blacklegged tick is
abundant during our warm weather months in hardwood and
mixed-hardwood forests of Minnesota. When a tick infected with POW
virus attaches to a person, it might take only minutes of tick
attachment for the virus to be transmitted.

POW was first detected in Minnesota in 2008, in a Cass County
child who was exposed near home. In 2009-2010, five additional POW
cases were identified in Minnesota. These cases were likely exposed
to infected ticks in north-central or east-central counties (Cass,
Carlton, Hubbard, Itasca, or Kanabec). In addition to these human
cases, MDH has found POW-infected ticks in northern counties (Cass,
Clearwater, and Pine) and in southeastern Minnesota (Houston
County).

POW virus was first described in 1958 in Powassan, Ontario.
Since then, about 60 cases have been identified in North America.
Most of these cases were from eastern Canada and the northeastern
U.S. until the last decade, when cases began to be reported from
Michigan, Wisconsin, and now Minnesota.

POW virus is related to West Nile virus (WNV). Like WNV, POW
virus can cause severe disease of the central nervous system,
involving inflammation of the brain (encephalitis) or the lining of
the brain and spinal cord (meningitis). People with POW may have
fever, headache, vomiting, weakness, confusion, loss of
coordination, speech difficulties, and memory loss. Signs and
symptoms occur within one to five weeks of an infectious tick
bite.

To prevent tick-borne diseases, always use tick repellents
containing DEET (up to 30 percent concentration) or permethrin when
spending time in tick habitat. Products with DEET can be used on
the skin or clothing. Permethrin-based products, which are only
applied to clothing, are highly effective and can last through
several washings and wearings. Also, wear long pants and
light-colored clothing to help detect and remove ticks before
they’ve had time to bite. People with homes or cabins near the
woods can also use landscape management and targeted pesticide
applications to reduce exposure to disease-carrying ticks.

After returning from outdoors, check your body carefully for
ticks and promptly remove any you find. The process of bathing or
showering shortly after returning indoors can help remove ticks
before they bite or before they’ve been attached for long.

The back end of the adult female blacklegged tick is
reddish-orange in appearance and teardrop-shaped. The nymph, or
immature, stage of the blacklegged tick is about the size of a
poppy seed and dark-colored. It is so small that it often goes
unnoticed. When the nymph is noticed, it is easily mistaken for a
speck of dirt or small freckle on people’s skin. Blacklegged ticks
are smaller and darker in color than American dog ticks (also known
as wood ticks). They also lack the dog tick’s characteristic white
markings. To remove a tick, use tweezers to grasp it by its head
close to the skin and pull it out gently and steadily.

More information about Minnesota’s tick-borne diseases,
including details on tick-borne disease prevention and pictures of
ticks, is available on the MDH Web site or by calling MDH at 651-201-5414.

 

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