The tick-borne Powassan virus – you don’t want it

No food or comedy this week. I felt this story was important enough to tell it straight. Also, this blog has a mind of its own… it does what it does.

Beyond Lyme – a nightmare tick virus

(Note: see May 1, 2015 UPDATE of this story, Powassan on the Rise, and also June 3, 2015 Powassan – a Survivor’s Story)


The Centers for Disease Control and Prevention list 14 diseases that people can get from tick bites. Many of them are regional, like Heartland virus in the Midwest and Colorado tick fever in the Rockies, but there are six that are fairly widespread and can infect people here in Maine. Lyme heads the list for its prevalence (it’s estimated that Lyme is carried by half of all deerticks, which are also known as blacklegged ticks) and for being at “top of mind” among people and the medical community here.

Lyme, a bacterial disease, has had plenty of attention among some of my fellow bloggers (including me) and also in the Bangor Daily News, and rightly so. It can make you very sick in the short term and spawn a host of health problems down the road. But the bacterium responds to aggressive antibiotic therapy, so many people make a full recovery after initial symptoms.

The tick-borne Powassan virus, on the other hand, doesn’t respond to anything.

Lyn Snow’s case

We were friends and neighbors of Lyn Snow and her husband Jack, whose house is just three doors up the road, and got together several times for dinner and other things, until Lyn took ill last November. She’d been out on a walk with a mutual friend, Jerry, and returned, unbeknownst to her, with a deertick lodged in her scapula. Two days later, she was sick enough to go to PenBay Medical Center, which found the tick, suspected Lyme and started intravenous antibiotics. She got progressively worse over the next few days, then became unconscious, and when her kidneys shut down she was transported to Maine Medical Center. She remained in a coma and was unresponsive to any stimuli. An EEG was performed, showing minimal brain activity.

About that same time – several weeks after the bite, her doctors sent blood samples to the labs at CDC’s Division of Vector-Borne Diseases in Ft. Collins, Colorado. Tests indicated the pathogen was either Powassan or a variant strain of it. Case closed. There was nothing to be done.

Some five weeks after being bitten, life support was discontinued and Lyn died the following day. She was one of only 50 people in the U.S. (and the fifth in Maine) ever to contract Powassan, and only the fifth to die from it. Her story was covered widely in the media statewide, including this newspaper.

The virus and its surveillance

Powassan virus, named after the town of Powassan, Ontario where the first case was identified in the late 1950s (a young boy who died after a tick bite), can cause symptoms similar to encephalitis, including seizures, brain swelling, and loss of consciousness, and in 10% of the cases, death. Half the patients who survive suffer permanent and debilitatingly severe neurological damage.

pow_us_human_map_week53(Cases testing positive for Powassan, 2013. Two fatal – in Poughkeepsie, NY, and here in So. Thomaston, ME)

As rare as it is, this is one very terrifying germ. It’s almost certainly in the woods around us, but it’s impossible to know just how prevalent it is. I spoke with Dr. Sheila Pinette, Director of Maine Centers for Disease Control in Augusta, and she added some important information: though the Powassan’s host (or vector) is the deertick, it’s believed the ticks come more frequently from woodchucks, mice, and squirrels than deer. Others have said the tick moves from the woodchuck to the deer, and then to humans. (See Maine CDC’s Powassan page here). What makes it all so sinister is that, unlike with Lyme-bearing ticks, there is no delay between the bite and the transmission of the virus. Once it bites you, you have the virus. Maine Medical Center has an excellent web page on this virus and other tick-borne pathogens.

Maine CDC and the University of Maine seek more information about ticks, and to do this they want your ticks in the mail! The better the surveillance, the more we know about the risk level in our area.*

pow_me_human_map_week53(Lyn’s case on a Powassan-positive map, 2013. Both maps from U.S. Geological Survey and Centers for Disease Control and Prevention)

I also spoke with Dr. Marc Fischer, epidemiologist at CDC’s facility in Ft. Collins. His specialty is arboviruses, a name derived from ARthropod-BOrne viruses (arthropods include insects, arachnids, and crustaceans – animals with an exoskeleton and a segmented body). Dr. Fischer also directs ArboNET, a CDC-sponsored national surveillance system for arboviral diseases in the U.S. ArboNET was established in 1999 to respond to the spread of West Nile Virus, but has since expanded to surveil any disease-causing virus from insects and arachnids (which includes ticks), like Powassan. But ArboNET is a passive surveillance operation: they don’t go out and collect ticks. They keep track of all arbovirus diseases reported to them by the medical community nationwide.

Dr. Fischer knew about Lyn Snow’s case with Powassan. He indicated that surveillance of tick-borne diseases – especially those that mimic the symptoms of encephalitis – is catch-as-catch-can. Some clinicians don’t find a tick bite and misdiagnose the disease. Others fail to report. But so far, it may be the best data collection effort out there.

Permethrin beats DEET

What to do? Any and everything possible to avoid tick bites. My wife and I bought several bottles of a permethrin clothing treatment, which is odorless and colorless: mix the solution in a large plastic bag, add four or five pieces of tightly rolled-up clothing you wear a lot in summer, seal the bag, and massage the liquid throughout the clothing. After it soaks for two hours, you can remove the clothing and run it through the dryer. Permethrin-treated clothes can be washed and dried several times without diluting the chemical’s effectiveness. It lasts a month or more. Then do it again! (The brand we bought is TickBlock, from Massachusetts).

Permethrin is hugely more effective than DEET at repelling and killing ticks. If a tick lights on permethrin-treated clothing, it will curl up, fall off, and die. Permethrin’s toxicity to humans is also very low: it’s used as an insecticide on fruits and vegetables, so we eat it all the time.

So that’s about it. Ticks are here in abundance, and we don’t know what they’ve got in them.


* When I wrote this piece, I knew about the University of Maine’s Tick ID program and its $10 fee per tick (along with its complicated shipping instructions). I agree with others that it’s absurd for the public to have to pay to participate in public health research. But the state funding cuts for public health under this administration left the University with no choice. I don’t have data yet on how many ticks have been processed through the program, but the submission process is so discouraging it can’t be very many.

(Wednesday, June 4 update): I’ve just heard from Griffin Dill, Integrated Pest Management Professional with the University of Maine Cooperative Extension Tick Identification Lab. He offers some detail about the tick ID program:

The Maine Medical Center Research Institute (MMCRI) ended its tick identification program in 2013, after 25 years of operation, due to lack of funding. To provide the people of Maine with an in-state resource for tick identification, University of Maine Cooperative Extension initiated a tick ID program this year. While MMCRI was and still is conducting public health research on ticks and tick-borne diseases, the UMaine Tick ID Lab currently only has the capacity to provide identification services. Unfortunately, funding limitations require us to charge a $10 fee to help defray the costs of this service. There will be a bond referendum on November’s ballot to provide funds for a new animal and plant lab for University of Maine Cooperative Extension. This new biosecure lab would allow us to screen ticks for disease, conduct tick research, and hopefully reduce or eliminate the fee for identifications.

I believe what’s needed is a stronger surveillance effort to identify pathogens within ticks (and other vectors) before they infect people, so we have a better sense of what’s out there, where, and what the risk is. Work at the new lab is headed in that direction. Thanks to Griffin for writing.


I want to thank Dr. Sheila Pinette, Director of Maine CDC in Augusta, and Dr. Marc Fischer, epidemiologist at CDC’s (federal) Division of Vector-Borne Diseases in Fort Collins, Colorado, for their help in preparing this piece.



Ned White

About Ned White

Ned White is a writer, novelist, crossword puzzle constructor, traveler through 49 states, and at times a danger in the kitchen. He lives with his wife in South Thomaston.