Minnesota records first death from tick-borne Powassan (POW) virus

Health officials emphasize the importance of preventing tick bites

Posted July 13, 2011

On June 29, the Minnesota Department of Health (MDH) issued a release stating a woman in her 60s from northern Minnesota died from a brain infection due to the Powassan (POW) virus, transmitted through the bite of an infected tick. This was the first death in the state attributed to the disease.

Another likely POW virus case was identified this year in an Anoka County man in his 60s who was hospitalized with a brain infection.

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. The POW virus is related to West Nile virus and can cause encephalitis or meningitis.

Six POW virus cases were identified in Minnesota residents between 2008 and 2010 according to the MDH.

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, MDH epidemiologist.

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

As a result of the state's government shutdown, an updated report on tick-related illness is not available through the Minnesota Department of Health, but the department continues to collect reportable disease data.

Tick season present

Dr. Larry Leadbetter, St. Joseph's Area Health Services Hospitalist and Infection Prevention Medical Advisor says that locally, clinic and Emergency Department physicians are seeing a noticeable number patients who have come in to be tested and/or treated for tick bites this summer, and a number of patients have been hospitalized as a result of tick-borne illnesses.

Tick-borne diseases of concern in Minnesota are Lyme disease, human anaplasmosis, and babesiosis. To a lesser degree in incidents are POW, Rocky Mountain spotted fever, southern tick-associated rash illness, human monocytic ehrlichiosis, and tularemia.

RaeAnn Mayer, St. Joseph's Community Health Manager, noted that last year, although most people associate Lyme disease with tick bites, anaplasmosis was the most prevalent tick-associated illness in Hubbard County with 35 cases reported.

She cited a report from the MDH's Infection Disease Epidemiology Prevention and Control (Jan. 1, 2010 ­ Dec. 31, 2010). Lyme disease accounted for another 31 cases diagnosed in the county. There were six cases of babesiosis reported, two with monocytic ehrlichiosis/anaplasmosis-ehrlichiosis undetermined.

Dr. Leadbetter said that a tick can transmit more than one illness at a time and that anaplasmosis so far seems to be appearing in greater numbers than Lyme disease again this year. It is being seen in people considered in good health as well as those who are immune-compromised.

If you have a question about a tick bite, or if you think you have a tick-associated illness, contact you primary care physician immediately. When examining patient tick bites, physicians take into consideration the possibility of infection as a result of injury to the skin.

The deer or bear tick

In Minnesota, POW virus can be transmitted by the blacklegged tick (also called the deer or bear 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 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 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.

Prevention is best

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. Remember to wear long pants and light-colored clothing to help detect and remove ticks before they have 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. Bathing or showering shortly after returning indoors helps 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.

Information about minimizing your risk of tick-transmitted diseases, protecting your pets, and removing ticks, is available on the MDH Web site at www.health.state.mn.us/divs/idepc/dtopics/tickborne/.