(Photo Credit- CDC)
# 5663
News today of the first known death in the state of Minnesota from the Powassan Virus (POW), a rare but sometimes deadly Flavivirus in the same family of arboviruses as West Nile Virus (WNV), Dengue Fever, St. Louis Encephalitis, and Yellow Fever.
Minnesota’s Department of Health has details on this fatality in the press release below, after which I’ll return with more on this rare infection.
News Release
June 29, 2011
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.”
The Powassan Virus (POW) was first identified in 1958 in Powassan, Ontario following the death of a child from the infection. Later, a species of ticks (Dermacentor andersoni) collected in Colorado in 1952 were shown to carry the same virus.
The virus can be transmitted by the same species of ticks that carry Lyme disease, anaplasmosis, and babesiosis (bacterial or parasitic infections).
The animal reservoir for the virus appears to encompass a wide range of mammals. According to the Canadian Cooperative Wildlife Health Center the virus has been identified with:
. . . the Woodchuck (Marmota monax) and the tick Ixodes cookei seem to be particularly important, but infection rates can be high in Red Squirrels (Tamiasciurus hudsonicus), Grey Squirrels (Sciurus carolinensis), Eastern Chipmunks (Tamias striatus), Porcupines (Erethizon dorsatum), Deer Mice (Peromyscus maniculatus), voles (Microtus sp.), Snowshoe Hares (Lepus americanus), Striped Skunks (Mephitis mephitis) and Raccoons (Procyon lotor).
Human POW infection appears to be very rare, but difficulties in testing, the variability of illness severity, and similarity of symptoms to other illnesses may be clouding that picture.
The Minnesota Department of Health advises:
How common is POW disease?
Physician-diagnosed POW disease is very rare. Fewer than 60 cases have been identified in the U.S. and Canada since 1958. From 2008-2010, six cases of POW encephalitis or meningitis have been reported in Minnesota. These cases lived in or had visited wooded areas in north central or east central counties (Cass, Carlton, Hubbard, Itasca, or Kanabec).
It is possible that other cases of suspected viral encephalitis or meningitis during times of peak tick-borne disease transmission (May to October) are due to POW virus.
In light of this fatality, the Minnesota Health Department is advising health providers:
- Medical providers should consider the possibility of POW virus infection in patients with central nervous system disease who have recent histories of activities in wooded areas (with or without known tick bites) during Minnesota’s warm weather months.
- The only laboratories that offer testing for POW virus are at state health departments (including MDH) and CDC. At this time, no commercial laboratories offer serologic testing for the virus.
- Serum or CSF specimens from patients with central nervous system disease can be submitted directly to the MDH Public Health Laboratory for arboviral disease testing, including POW virus.
Complicating matters, the state of Minnesota is facing a potential shutdown of government services at midnight tonight due to a budget impasse that could adversely affect state laboratory testing services.
Admittedly, the odds of contracting the Powassan virus are exceedingly low. More people are struck and killed by lightning each year or killed by bee stings.
But when you consider the wide panoply of tickborne diseases found in the United States;
Lyme disease, anaplasmosis, babesiosis, TBE (tick borne encephalitis), Rocky Mountain Spotted Fever, Ehrlichiosis, STARI (Southern Tick-Associated Rash Illness), Tickborne relapsing fever (TBRF), Rickettsiosis, and Tularemia . . .
. . . well, the odds of getting sick from a tick bite go up considerably.
Lyme disease alone is considered responsible for 20,000+ infections each year (MMWR Lyme Disease --- United States, 2003—2005).
Which means that preventing tick bites, and looking for and removing ticks as quickly as possible, are important steps to take after visiting tick-endemic areas.
Since it is summer, and tick season, a few timely reminders:
Lastly, the CDC offers the following advice:
Preventing Tick Bites
While it is a good idea to take preventive measures against ticks year-round, be extra vigilant in warmer months (April-September) when ticks are most active.
Avoid Direct Contact with Ticks
- Avoid wooded and bushy areas with high grass and leaf litter.
- Walk in the center of trails.
Repel Ticks with DEET or Permethrin
- Use repellents that contain 20% or more DEET (N, N-diethyl-m-toluamide) on the exposed skin for protection that lasts up to several hours. Always follow product instructions. Parents should apply this product to their children, avoiding hands, eyes, and mouth.
- Use products that contain permethrin on clothing. Treat clothing and gear, such as boots, pants, socks and tents. It remains protective through several washings. Pre-treated clothing is available and remains protective for up to 70 washings.
- Other repellents registered by the Environmental Protection Agency (EPA) may be found at http://cfpub.epa.gov/oppref/insect/.
Find and Remove Ticks from Your Body
- Bathe or shower as soon as possible after coming indoors (preferably within two hours) to wash off and more easily find ticks that are crawling on you.
- Conduct a full-body tick check using a hand-held or full-length mirror to view all parts of your body upon return from tick-infested areas. Parents should check their children for ticks under the arms, in and around the ears, inside the belly button, behind the knees, between the legs, around the waist, and especially in their hair.
- Examine gear and pets. Ticks can ride into the home on clothing and pets, then attach to a person later, so carefully examine pets, coats, and day packs. Tumble clothes in a dryer on high heat for an hour to kill remaining ticks.
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