On the Fourth of July weekend in 2012, Alan Bergo and a friend were bushwhacking through a forest near Crane Lake in northern Minnesota, foraging for morels and boletes. A sous chef at the now-closed Heartland restaurant in St. Paul, Bergo was on break from work, indulging his obsession for mushroom hunting. He wore a little bug spray in the woods that day, and thought nothing of it when he picked a few ticks off his clothing.

A week and a half after his jaunt, on a Tuesday, Bergo felt dizzy and lethargic, with a pounding headache. He popped some ibuprofen, drank a lot of coffee, and went to work. That night he had sweats and then chills. On Wednesday, the executive chef saw how pale and sick he was and told him to go to the emergency room. He told the doctors about his symptoms and that he had been in the woods searching for mushrooms. They let him go without meds and said he must be getting over a bug. A few days later his left eye became bloodshot and he noticed four red rashes on his chest and stomach. Suddenly it hit him—he might have Lyme disease.

Bergo's hunch was confirmed within days after a visit to a physician's assistant, who ordered a test that came back positive for Lyme. He was prescribed antibiotics, but for weeks he endured more symptoms, including deeper lethargy, a loss of mental focus, cluster headaches, and Bell's palsy—a temporary paralysis of half of his face, which sent him to a neurologist.

The Bell's palsy gradually faded, but he had foggy thoughts for weeks. Still, three weeks after he was diagnosed, Bergo went back out into the woods.

"It was in the middle of mushroom season. I wasn't going to miss the end of it," he says. "I was like, ticks be damned."

Bergo began to take new precautions, though. He wore clothes treated with the pesticide permethrin, did a thorough tick check after foraging, and took a shower when he got home. He now goes out more than ever. Prevention isn't the only change he's made. "I would say the biggest change in my thinking about ticks is how much I warn other people now," he says.

Lyme disease in Minnesota is on the rise. In the past five years the state has averaged more than 1,200 reported cases a year, up from fewer than 300 two decades ago. Multiple factors have caused the increase, including warmer winters that allow ticks to stay out longer; habitat changes that allow ticks to flourish; and an increase of host populations, such as deer and mice.

In one of nature's crueler twists, the impact of Lyme has been especially pronounced among Minnesotans who spend time in nature. People who play and work outdoors have grown especially used to swapping tales of tick-borne Lyme infections—who has one, who had one, and how they can all prevent the next one. As the disease has spread, so has awareness.

Minnesota resident Andrew Vavra contracted Lyme five years ago while fishing in northeastern Wisconsin. He never saw a tick, but after being sick for more than a week with night sweats, aching joints, and sleeplessness, he found the characteristic bull's-eye rash on his thigh. He got treated and resolved not to let the disease affect his time outdoors in Minnesota. Today, he wears DEET insect spray on his clothing and checks himself and his dogs carefully after every outdoor excursion.

"It's so incredibly preventable if you take it seriously," says Vavra. "It takes five minutes to make sure that you don't tank your physical and mental well-being for the long term."

In Minnesota, Lyme disease is carried by the blacklegged tick, more commonly known as the deer tick. Bites from tick nymphs account for the greatest number of Lyme cases in the state. This immature stage is active primarily between May and July, when about 20 percent of nymphs carry the bacteria that can cause the disease. Because of their size, roughly that of a poppy seed, these bites tend to go unnoticed and represent the greatest number of Lyme cases. Adult ticks, about the size of a sesame seed, also bite people and can carry the bacteria that can cause the disease throughout much of the year. Some 40 percent of them carry Lyme.

In the early to mid-1980s, researchers found blacklegged ticks primarily along the Minnesota and Wisconsin border from the Twin Cities to Duluth. Now they're finding them in high numbers in southeastern Minnesota, north-central Minnesota, and northwestern Minnesota. Department of Health epidemiologist Dave Neitzel, who has surveyed for ticks in Minnesota since the 1980s, tells people that they should be aware of blacklegged ticks when they go out in any deciduous and mixed deciduous forest habitat in the state. The rotting leaf litter on the forest floor and surrounding grass and shrubs provide the warm, humid environment the ticks prefer. Two key hosts, white-tailed deer and white-footed mouse, also thrive in this habitat.

That's indeed where many shared stories of Lyme infection begin.

Retired Department of Natural Resources mentoring program coordinator Mike Kurre first contracted Lyme disease 15 years ago. He was cutting brush on his property just south of Mille Lacs Lake. A few days later he saw the telltale bull's-eye rash. Kurre got treated and started spraying his clothing with permethrin, which incapacitates ticks on contact. He also began tucking his pants into his socks and doing tick checks at the end of every day. His DNR work, which included advising others about tick safety, took on a new personal urgency.

Three years ago, though, Kurre briefly let down his guard. One day in April he went out to split wood on his property. Because snow was still on the ground, he didn't take any precautions. A few days later he had all of the symptoms of Lyme except the bull's-eye rash, and a test confirmed the disease. Now he's vigilant whenever he's outside. "When the sun comes out if there's moisture or snow on the ground, I've flicked them off deer hunting many times," says Kurre.

Neitzel says milder and wet winters due to climate change have created an environment for ticks almost year-round now. Ticks had previously had a reputation for being out from late spring through the middle of the summer and then the fall. Now January is the only month in which Neitzel hasn't seen an active blacklegged tick, though they are still more common in the warmer months.

"Warmer conditions just help them to have a longer growing season and maybe a greater chance to find hosts in some of the life stages too," he says.

Minnesota Deer Hunters Association executive director Craig Engwall has contracted Lyme disease three times, one of them while hunting in November. The first time, he was at his home about an hour north of Grand Rapids when he took off his watch to do the dishes. On his wrist he saw a small dot the size of a pinhead—a nymph. He removed the tick, which he guessed he got from petting one of his two Labrador retrievers, and three days later he felt terrible, with aching joints. He was treated for Lyme, but symptoms persisted. Later, he found out he also had babesiosis, a disease with similar symptoms spread by blacklegged ticks.

"I have friends up here, particularly older ones, who even get worried about ticks when going into their gardens," says Engwall. "But I won't give up anything. I just prepare for it."

As part of his job raising awareness about Lyme disease for bird hunters, DNR forest game bird coordinator Ted Dick encourages people to talk to their vets about treatments that might include a topical liquid so the pets don't act as tick carriers and a dog vaccine so the animals don't get Lyme. Chad Hines, a kennel owner and bird hunter, has had Lyme disease three times. His wife, Tracy, has had it too. They wear permethrin-treated chaps and clothes, treat their dogs with a topical liquid, and cut orange, permethrin-treated cattle tags in half and place them on their dogs' collars and on their ATV. They also perform prescribed burns and stick to the trails on their property near Little Falls to reduce the chances they, their kids, or their dogs will pick up ticks.

"The more I understand about them, the easier it is to get around them," says Hines.

Public health experts agree that Lyme disease is underreported for a variety of reasons, including missed diagnoses by doctors, a lack of awareness by patients, and treatment by doctors who may not always communicate their findings to the Minnesota Department of Health. The disease also shows no signs of slowing down and isn't the only tick-borne illness increasing in the state. Cases of anaplasmosis, a bacterial disease also carried by blacklegged ticks that causes fevers, headaches, muscle aches, chills, and shaking, rose from less than a few dozen a year in the mid-1990s to an average of more than 600 a year since 2010. Reported cases of babesiosis have increased from less than four a year in the mid-'90s to more than 50 a year since 2010. The Minnesota Department of Health lists eight tick-borne diseases in people, though most occur at low numbers. Still, the number of diseases found in the state may increase, says Mayo Clinic researcher Dr. Bobbi Pritt.

"It is likely that other tick-borne pathogens have yet to be discovered," she says.

With tick-borne disease expected to increase in the state, there are no options for widespread control. People sometimes put cardboard tubes containing permethrin-treated cotton balls in their yards. Mice take the cotton balls back to their nests for insulation and the permethrin kills the ticks. There are also deer feeding stations with permethrin-treated rollers that transfer the pesticide to the ungulates as they go in for corn. But neither of these measures is feasible on a large scale. Nor is large-scale spraying for ticks is not an option. "How do we know that the agent would penetrate deep down enough in the leaf litter?" says University of Minnesota tick scientist Ulrike Munderloh. "We would also affect a lot of other invertebrates that are beneficial for us, including, particularly, spiders."

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The Minnesota DNR, which has more than a thousand employees who work out in the field, has focused on preventive measures as a key to reducing cases. The agency offers a tick resource guide on its internal website that goes over the value of using permethrin, identifies the habitats where ticks thrive, shows how to conduct daily tick checks, and shares how to recognize the symptoms of disease. Field employees attend informational talks and webinars and are eligible to get free permethrin-treated clothes, which the DNR views as the primary control method against tickborne illness.

"It is one of our major occupational health risk exposures," says DNR safety administrator David Palet. "I don't think this is something that is going to go away, and the potential risk of contracting a tick-borne illness is likely only going to increase over time."

Minnesotans have shown that with this knowledge they will continue to go out. In a 2010 survey of ruffed grouse hunters by the University of Minnesota, more than 40 percent said they worried about contracting Lyme, but less than 10 percent said they don't hunt as much or have changed where they hunt because of the disease. State parks do tick talks for visitors, post tick safety flyers on bulletin boards, display vials of ticks, and provide tick identification cards. The Metropolitan Mosquito Control District posts signs at dog parks and puts brochures, tick cards, and posters at 292 locations.

Sammie Peterson, a 31-year-old naturalist at Quarry Hill Park and Nature Center in Rochester, contracted Lyme disease in 2012—likely while traveling around the state with Conservation Corps. She worked a lot in the woods and taught children about outdoor activities through a Conservation Corps and DNR program called "I Can Camp!" She took few precautions against ticks and frequently pulled them off her body. Then she contracted a bad case of Lyme. Now she wears permethrin and tells students to check for ticks when she gives tours through long grass, an important step since children ages 5 to 14 account for the highest number of reported cases.

"I explain to them that as residents of Minnesota, this is something they should do as a habit, and that as long as they are checking themselves to remove ticks before they bite, they should be fine," she says. "My approach is just matter-of-fact. I try to be really careful to frame it in a way that doesn't induce hysteria, since my main professional goal is to connect people to the natural world, to help them feel comfortable, safe, and confident interacting with the outdoors."

There's also a growing awareness among health-care professionals, especially those working in children's summer camps. Linda Erceg, the chair of the Healthy Camp Initiative, says camp nurses have changed the way they respond to the disease. When camp nurses in Minnesota find a suspicious tick on a camper, they often work with the camp's physician and give a dose of an antibiotic. If, however, symptoms of Lyme disease emerge, they send their campers to a clinic. Doctors in the state have become more aware of the disease, though some patients interviewed for this article said they needed to advocate for themselves.

As part of her job as a tick specialist for the Metropolitan Mosquito Control District, Janet Jarnefeld has surveyed the seven counties around the Twin Cities for more than 25 years. In that time, she has witnessed deer ticks spread south and west through every metro county and stay active longer with the warmer weather. She still encourages people to get outside in tick habitat.

"We're all tough Minnesotans and we know we want to enjoy the outdoors," she says. "Don't be afraid of it, but do follow precautions for ticks in woods and brush where deer ticks are located."

Editor’s note: Use permethrin and other insecticides only as directed on the label. For more information on ticks and the prevention of tickborne diseases, check out the Minnesota Department of Health website.