Wednesday, November 18, 2015

Adirondack Lean-tos, Mice and Hantavirus

Sand Lake Lean-toLean-tos provide some of the comforts of home in the Adirondack backcountry – a respite from inclement weather, and a comfortable place to cook, eat and socialize. Unfortunately, a potential hidden danger lurks in every corner, and hikers may be unintentionally contributing to the problem.

The threat is the Hantavirus, a nasty virus in the Bunyaviridae family. These viruses infect, but leave unharmed, a variety of local rodent species.  Unfortunately, the virus can produce a potentially fatal disease in humans, brought about by contact with rodent urine, saliva or feces. Deer and white-footed mice are frequent visitors to Adirondack lean-tos.

This is no late Halloween horror story; the possibility of Hantavirus is not unheard of in the Adirondacks. Several years ago, a hiker bitten by a mouse in a lean-to may have contracted an infection from the deadly virus. Despite my own skepticism about this particular incident, the potential for an infection exists in the Adirondacks. Based on what I witnessed at a couple lean-tos this past summer, this risk may be growing.

The Hantavirus risk became apparent to me during a late summer trip into the Five Ponds Wilderness. Unlike my usual backcountry trips, this was no bushwhacking jaunt; instead, old logging roads, unmarked herd paths and a few state marked trails provided access to areas I had not visited for several years. The lean-tos at Sand Lake and Wolf Pond provided comfortable accommodations.

Lean2Rescue rehabilitated these same lean-tos some years ago and mostly cleaned them out, including clearing everything underneath. They used to have an odd assortment of junk stuffed under there – everything from discarded underwear to bundles of sticks.

This clean-up did more than just make the lean-tos a more attractive place to camp, it also made them less attractive to mice. Without the cover of branches, old footwear and other assorted debris, these shelters became much less hospitable to mice, reducing the probability of inhaling their potentially Hantavirus-laced urine and feces.

Unfortunately, people are once again stuffing things underneath these lean-tos. Branches, twigs and other woody debris are once again finding their way under these lean-tos, or in the case of Wolf Pond, in the lean-to itself. Although it may feel conscientious to others arriving later, woody debris should not be left under or in a lean-to, where it produces conditions where mice can feel comfortable and secure.

Wolf Pond Lean-toThis wasn’t an immediate concern of mine until I returned home. It appears I brought something back other than duff, photographs and memories. Within a week of my trip, a nasty virus invaded my respiratory system. My hypochondria engaged, and I thought: Hantavirus!

Cluttering-up the space underneath the lean-to was not the only way hikers are courting possible danger with Hantavirus. Between the two lean-tos I stayed at there was a pair of tennis shoes, a tangle of nasty smelling rope and some shredded toilet paper. These articles provide shelter  and insulation for mice.

In my many years of trail hiking, I never left anything behind in a lean-to. Some people may think it is considerate to leave behind unneeded toilet paper, matches, foodstuffs and other assorted items, but in reality they are just providing rodents another excuse to put up shop and spread their urine and feces in a place where other hikers will be sleeping.

Removing the shelves within lean-tos would probably alleviate much of this problem, thus reducing convenient places to leave stuff behind. It appeared this solution was attempted in the Sand Lake lean-to, but unfortunately, someone wedged in two-by-fours to provide makeshift shelving. Leave no Trace principals should also apply to stuff left behind in lean-tos, including so-called improvements.

Brooms are often found in lean-tos, but sweeping out a lean-to could put someone at serious risk of catching Hantavirus, as it aerosolizes dried mouse urine and feces.  Lean-tos should probably be swept only just before leaving (as long as no one is waiting to use it). Using only long-handled brooms might provide some added protection, as would wearing something over your nose and mouth as a filter for aerosolized particles of mouse feces and urine that may contain Hantavirus. Either that, or avoid sweeping altogether.

If an outbreak ever arises from Adirondack lean-tos, it may be necessary to take even more extreme steps like sanitizing remote lean-tos or even removing them altogether. I hope such extreme measures would never be necessary.

Unfortunately, the habits of many lean-to visitors are making these shelters more hospitable to mice that may carry the deadly Hantavirus. We should all adopt a new lean-to etiquette, rather than jeopardize the lean-to tradition we all enjoy.


Not to mention, that it would also reduce the anxiety around this issue for all of us backcountry hypochondriacs.

Photos by Dan Crane: Sand Lake and Wolf Pond lean-tos.

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Dan Crane writes regularly about bushwhacking and backcountry camping, including providing insights on equipment and his observations as a veteran backcountry explorer. He has been visiting the Adirondacks since childhood and actively exploring its backcountry for almost two decades. He is also life-long naturalist with a Master of Science in Ecology from SUNY ESF and 10+ seasons working as a field biologist, five inside the Blue Line.

Dan has hiked the Northville-Placid Trail twice and climbed all 46 High Peaks but currently spends his backpacking time exploring the northwestern portion of the Adirondacks. He is also the creator of the blog Bushwhacking Fool where he details his bushwhacking adventures.

14 Responses

  1. Paul says:

    How about the DEC recruit a cat for each lean-to? Good story. For now I think the risk in this area is still pretty minimal if anything. Even in places where it is more common it is still very uncommon.

  2. Bill Ott says:

    This is completely new stuff to me, and probably a lot of other back woods campers. I visit shelters to read and write in the log books. Sometimes I stay overnight, on the ground outside, unless it rains. A shelter can be a life-saver in a bad storm.
    I have often wondered how people thought it was OK to grace these shelters with useless crap (like shovel heads). And mice bite through the toilet paper baggies. Now, after reading this post, I will feel justified in decrapping whatever I can whenever I can, and that will be soon. I love a mission!!
    Thanks for this post.

    Bill Ott
    Lakewood, Ohio

  3. Justin Farrell says:

    Good story, thanks for sharing.
    Just to share a thought…
    Hantavirus is definitely no joke!
    Unfortunately, even when shelves have been removed in certain lean-tos, people still seem to leave things behind, including garbage, or even extra firewood where mice may end up nesting….The same things that people who own camps need to be careful of.
    It’s a sad fact, but many Adirondack lean-tos should really just be gone already. Too many people seem to rely on a lean-to for their shelter, and do not take the proper precautions to bring their own shelter, which can often lead to a lean-to being overused, as well as being more prone to violations of DEC regulation & LNT principles, and other public concerns like Hantavirus.
    For what it’s worth, in 30+ years of visiting the Adirondacks, I’ve yet to see a fresh roll of TP and an unopened can of soup left behind at a tent site.

  4. Chuck Bergquist says:

    “If an outbreak ever arises from Adirondack lean-tos, it may be necessary to take even more extreme steps like sanitizing remote lean-tos OR REMOVING THEM ALTOGETHER.”

    So, if a case of hantavirus is discovered within the bounds of NY at some point in the future, the epicenter will undoubtedly be a Lean2. Of course, that’s the only possibility. There simply cannot be any other, for the virus vector is only found there and nowhere else.

    While we’re taking out the Lean2’s, can we also take out all the mud, rocks, roots and every other trip and slip hazzard from all the hiking trails? Year after year these menaces are the cause of nearly all of the many thousands of hiking related injuries. How often do we hear of backcountry rescues because of slips and falls? This danger is real, its here, and something can be done now.

    If it’s discovered that driving one’s car to the trailhead poses a greater potential threat to human life than hantavirus, can this incredibly dangerous activity also be “removed”?

    While we’re at it, we should insist that every mouse in the state be trapped and tested for hantavirus periodically.

    Going on out on a limb here, but I’ll venture a guess that there are other places with higher mouse densities than Adirondack Lean2’s, like cities.

  5. George says:


    You never posted if you actually caught the Hantavirus or not. If you did, what happened?

    • Dan Crane says:


      Ooops, I forgot to mention how that turned out. It apparently was just a head cold. I recovered in a couple weeks.

      • Paul says:

        Glad to hear you are alright. We kinda figured you survived since you wrote the article!

        I have so many mice in my camp, if this virus comes here I’m toast!

    • Avon says:

      That was my thought exactly.
      Not only did I already start wondering when Dan wrote that “deer and white-footed mice” are rodents, but I noticed that there has never been a confirmed case of hantavirus in the backwoods.

      I too am glad that Dan now says it turned out to be just a head cold, but there is a line between hypochondria and news reporting – and “forgetting to mention” that the disease doesn’t exist in lean-to’s – even while proposing to remove them all – crosses that line!

      I’d rather have had this story appear as musings or commentary, rather than a serious report or warning. You never know – internet readers especially might just get all worked up over stuff like this once in a blue moon! (ahem.)

      • Dan Crane says:


        If you clicked the link (at “my own skepticism”), you’d find an article where a case of hantavirus was attributed to a lean-to in the High Peaks Wilderness. I had my doubts about it (which you’ll find in the linked article), but others at the time indicated that the disease most likely DID come from a mouse bite in a lean-to. Confirmed? Maybe not, but the risk of the hantavirus is present as long as mice and humans are in close proximity to one another. If people keep cluttering up the lean-to with their wood and refuse, the risk can only increase.

        As far as I am concerned, everything I write here is a musings or commentary. I am not a professional journalist, and I have never presented my writing at the Almanack to be serious news. This article was based on a recent anecdote that I thought the readers would find amusing.

        Obviously, you did not.

      • Dan Crane says:

        In addition, I NEVER proposed removing lean-tos, I merely stated that was a possible extreme measure that might be taken if hantavirus ever did become an issue. I even followed that up with “I hope such extreme measures would never be necessary.”

        Apparently, some were so incensed that I mentioned the possibility of removal that they did not bother to read the next sentence.

  6. Jesse B says:

    Dan, I’m a longtime reader and big fan of your articles, but I feel this one really misses the mark. As a public health scientist, I can say with certainty that Hantavirus, while connected to the Adks from a 2012 exposure, is rare. Very rare! Since 1993, only 5 reported cases have been from NYS and only that single exposure from the Adirondacks. And as with all zoonotic disease and a world of global travel, it is very difficult to ascertain a source of infection from 1 or 2 time-separated events. Considering how strongly you defended a precautionary approach to black bear attacks back in 2012 (e.g. attacks are rare, let’s not rush to pack firearms into the woods), you’re taking almost an opposite tack here with a disease that is arguably RARER than a black bear attack.

    While it is certainly great to promote good hygiene and camping manners when using a public lean-to, I’m sure the risk of hypothermia and exposure from removing them would far outweigh any risk of hantavirus infection. Once infected, hantavirus is a nasty disease, especially to at-risk populations, but it is also important to not inadvertently panic people over a disease they have an extremely low likelihood of acquiring in the upstate NY region. I’ll just chock this one up to your aforementioned hypochondria and will look forward to reading your next article!

    PS. White footed mice are the #1 reservoir of black legged ticks that host the Lyme Disease bacterium. That would be a much better disease-risk reason to not attract rodents to your lean-to.

  7. Judy says:

    This information should be posted at every lean-to. Judy

  8. Mike says:

    Go to an Adirondack lean to and you will surely perish as a result of exposure to the white footed mouse. Especially if you sweep it! Hantavirus is the “plague” of our time for sure. Scores have died… no wait the reality according to Jesse is that actually no one has, and there has only been one case of it even attributable to the Adirondacks in recent years. But I guess Dan figured he’d see how many folks he’d scare anyway, just for fun!

  9. John says:

    Hantavirus is really, really rare. And, it’s even more rare than that in the northeast. According to the CDC there have been 3 cases in NY from 1993 to 2014. One of those in the Adirondacks. The vast majority occur in the desert regions of the southwest. This is probably due to the drying effect on the mouse feces causing it to powder and spread more easily. That said, rodents and garbage spread all sorts of other diseases that are much more common. So your prevention points are well taken. One question is has there been any thought to signage in the leantos reminding folks not to leave things behind? Also, like influenza transmission commonly occurs when you bring contaminated hands close to your mouth and nose. This is also true of most other diseases. So, your mom was right. Wash you hands often especially after cleaning a leanto. That’s more important than any mask.