The fever started on a Monday morning in June. By Friday, I woke up in a bed at Mount Auburn Hospital in Cambridge, Massachusetts, with yellow skin, an inflamed liver, a dull pain in my stomach and a doctor offering me morphine.

A rotating cast of specialists, residents and medical students began streaming past my bedside as I cowered under a mass of towels and blankets trying to hide from sunlight that was causing my head to throb. Their best guess was that a gallstone was causing bacteria to build up in my bloodstream.

A surgeon recommended a procedure to clear any blockages, sort of like a “Roto-Rooter,” he explained, a tad too cheerfully. Then my temperature spiked to 104. If some sort of medical device snaking through my insides could bring relief, I wanted it, now.

Just six days earlier, my wife Rachel and I had celebrated our ninth wedding anniversary watching a dance performance in Harvard Square, less than half a mile from where I lay. Now—after a week of sweat-soaked nights, a full-body rash, episodes of vomiting and violent, shaking chills—Rachel stood anxiously by my bedside, helping me pry my wedding band off my swollen finger as I prepared for surgery.

When I came to in the recovery room an hour later, but it wasn’t because of anything the surgeon had done, he confessed. There was no blockage to clear. He didn’t know what explained my symptoms, but he did know one thing: Something was wrong with my liver.

Something was also wrong with my spleen, but that was an old story—I had had it surgically removed before I entered grade school. I mentioned this to the parade of doctors who saw me before and after surgery. In one of them—Vito Iacoviello, the hospital’s head of infectious diseases—that piece of my medical history had set off alarm bells and led him to make a quick decision that might have saved my life.

By the time Iacoviello saw me soon after surgery, the results of some initial blood tests had come in, including one for babesiosis, a rare tick-borne disease transmitted by the same tick that carries Lyme disease. He had seen dozens of cases of babesiosis over the years, and he knew how quickly the disease could progress, especially in someone without a spleen. If I was suffering from babesiosis and my condition got much worse, an aggressive form of blood filtering called plasmapheresis might be all that kept me from a coma.

The test for babesiosis came back negative, but Iacoviello started treating me for the disease anyway.

“Given the potential severity of babesiosis in a splenectomized patient, and even though his first smear is negative, I would feel more comfortable covering for this,” he wrote in my patient notes that day.

Follow-up tests later confirmed what Iacoviello suspected; I was indeed suffering from babesiosis. It is a potentially fatal parasitic infection carried by the blacklegged tick (more commonly known as a “deer tick”).

In my case, the tick probably had caught a ride on my pants a couple of weeks earlier as I led my two young children through a field at a nature center outside Boston. When it bit me and delivered the parasite it was carrying into my bloodstream, what resulted was a harrowing experience that gave me an all-too-intimate view of the growing epidemic of tick-borne disease in the U.S. today.

The spread of these illnesses has been fueled in part by climate change. Warming temperatures have played a key role in the steady rise of tick numbers and northward expansion of their range, all of which has helped give rise to what some are already calling the worst tick season ever.

Babesiosis, also known as “Nantucket fever,” is caused by the parasite Babesia microti, similar to those that cause malaria. It was first detected on the island off Massachusetts in 1969 and has since spread across much of New England and the northern Midwest. Most people with babesiosis never know they have it. For those with weakened immune systems, however, the infection can be deadly.

Lacking a spleen put me in that danger zone, since the spleen plays a key role in the immune response against blood-borne infections like babesiosis. My spleen had been removed when I was 4 years old as treatment for a rare blood disease, spherocytosis, that I inherited from my dad. The disease makes my red blood cells more sphere-shaped than disk-like, raising the potential for my spleen to not recognize and attack my own red blood cells. Such episodes had plagued my father before he was diagnosed, leading to bouts of jaundice and weakness to the point where he couldn’t walk.

I suffered no such attacks as a child, but, once my spleen was removed, I was vulnerable to infections and vigilant about always carrying an arsenal of heavy-duty antibiotics when traveling abroad. I knew how quickly a pathogen could overwhelm my system.

That’s what was happening now. Without a spleen to fight off the parasite, the Babesia had entered my bloodstream and begun to decimate my red blood cells. My yellow, jaundiced skin and urine that had turned a dark amber were symptoms of this full-scale assault.

Iacoviello started treating me with antibiotics for babesiosis Friday afternoon soon after surgery but I wasn’t out of danger yet. My fever never returned, but my skin turned more and more yellow. By Saturday morning, my urine looked like root beer, and I was put on oxygen as I was increasingly out of breath. A scope that had been pushed down my throat during surgery had left a slight perforation on the wall of my intestine, meaning additional antibiotics and no food for several more days. I hadn’t eaten since Wednesday; from the time I entered the hospital to the time I left one week later, I would lose 10 pounds.

On Saturday afternoon, as I lay in my hospital bed overlooking the Charles River, my doctor informed me that my lungs had partially collapsed and were beginning to fill with fluid. He didn’t seem too concerned and, with my fever gone, neither was I. I offhandedly mentioned the lung issues to Rachel, who relayed the information to my mom. It wasn’t until Monday morning, when, after both had visited with tears in their eyes, that I started to realize how serious my condition had been.

Alone with my laptop on Monday afternoon, I started Googling babesiosis and came across a study from Europe that reported roughly half of all patients with babesiosis, most of whom lacked a spleen, died from the disease. The North American strain of Babesia isn’t nearly as potent, but even in the U.S., the mortality rate for those with weakened immune systems, myself included, is still high, roughly 20 percent of hospitalized patients. As the numbers sunk in and I realized how close I’d come to dying, I set down my laptop, put my head in my hands, and sobbed.

Additional medication in the coming days helped drain the fluid from my lungs and, as the antibiotics took effect, my liver and lungs slowly recovered. It helped that I was only 40 years old and, except for the lack of a spleen, relatively healthy and physically fit.

My parents happened to be visiting when I fell ill, and it was comforting having them around while I was hospitalized. My dad is a retired physician and had been preparing me for the possibility of an event like this since I was young. When people without a spleen get sick, he would tell me, they have the potential to get really sick. Of his six biological children, four of us have spherocytosis and have had our spleens removed. (My own two children are, thankfully, unaffected.)To this day, he makes sure that all of us are current on the additional vaccinations we need to take throughout our lives.

I was often overwhelmed by the gaggles of medical professionals who would descend on my room at once, not sure who was who, not sure who I should focus my limited amount of energy on as I explained for the umpteenth time my medical history and what my symptoms were.

When I vented about this to my dad, he let me in on a secret. “Look at their coats,” he said. Medical students wear short, hip-length white coats, he told me. Doctors wear coats that come down to their knees.

About a week after I got out of the hospital, I took my kids to a nearby park for a picnic dinner with some friends from the neighborhood. Everyone was talking about their plans for the weekend: a trip to the Cape, hiking in Vermont, berry picking in the suburbs, areas that I now knew were all, literally, crawling with ticks.

After what I’d been through, their plans sounded so dangerous, even reckless. I jokingly tried to warn them, urge them not to go. Only I wasn’t really joking.

More than 300,000 Americans will be infected with Lyme and other tick-borne diseases this year, up from fewer than 15,000 confirmed cases in the 1990s. The cost of treating them is roughly $1 billion per year, leading one U.S. senator to call tick-borne diseases an “epidemic-like scourge.”

Epidemiologists knew as early as two years ago that 2017 would be especially bad. High acorn production in New England, ground zero for tick-borne disease in America, triggered an increase in mouse reproduction last year. With mice being a major transmitter of Lyme and other tick-borne diseases —they harbor the pathogens in their bloodstream, and infect almost every tick that bites them—it followed that this year would be a big one for Lyme and other tick borne diseases.

But other, longer-term changes are afoot.

“Over a 15-year period, the range of Lyme disease in human populations has doubled or tripled,” Richard Ostfeld, a senior scientist at the Cary Institute of Ecosystem Studies in Millbrook, New York, said. “I don’t know of any other diseases in which a sustained trajectory like that has been observed.”

Climate change might play a role in this spread in two ways. As warmer temperatures spread northward, ticks are moving northward, too. Researchers started finding blacklegged ticks in large numbers in Canada beginning in the early 2000s.

“Higher temperatures appear to be a key factor affecting where, and how fast, ticks are colonizing new localities,” researchers concluded in last year’s National Climate and Health Assessment.

Lyme disease in Canada followed close behind, with official reports climbing from 144 cases in 2009 to nearly 1,000 last year, though the actual number of infections are likely much higher.

“It’s gone from being a ‘well, that might happen’ to a reality,” said Nick Ogden, director of the Public Health Risk Sciences Division for the National Microbiology Laboratory of the Public Health Agency of Canada.

In addition, warmer temperatures give ticks, which are only active when temperatures are above freezing, a better chance to survive to adulthood and reproduce. Ticks go through three stages in their two-year life cycle: larva, nymph and adult. At each stage, they need to feed on the blood of a host organism, such as a mouse, a deer or a human, before they can move on to the next stage.

“They are basically going to drop dead within two years,” Ostfeld said. “They need to find three hosts within that time, and it is beneficial for them to have that longer warm season.”

My experience with babesiosis was enough to make me want never to venture outside again. But that’s no way to live. I often think back on what one member of Iacoviello’s team told me before I was released from the hospital: Don’t sacrifice doing what you love. You can go into areas with ticks, just take precautions.

Now, when I’m planning an outdoor activity I carry a change of clothes, from shoes and socks to pants to long-sleeve shirt, that are treated with permethrin, a powerful insect repellent that kills ticks on contact—and, hopefully, won’t cause cancer. I was initially terrified of walking across a mowed lawn or sitting on a blanket in the park. But whenever I’m concerned that I might have been exposed, I check myself for ticks before I go to bed. With each passing day, I’m a little less afraid.

My brush with death has affected my daily life in one other small way. While in the hospital, as nurses took blood samples or adjusted my IV early each morning, I’d watch rowers make their way up and down the Charles River, and I vowed that when I got out, I would join them. I now row twice a week, just a couple of river bends upstream from the hospital, as part of a learn-to-row class. I’m getting better at it, though I still often end up swimming next to my overturned boat rather than rowing in it.

This weekend, I’ll take my 6-year-old son on his first remote camping trip on a lake straddling Maine and New Hampshire. It’s a trip I’d been looking forward to for the better part of a year, then spent much of the summer trying to get out of.

Now, I’m ready. We’ll take a few precautions to meet the challenges of our rapidly changing world. But with a little luck, the biggest scare my son and I have will be from the ghost stories we’ll tell sitting around the campfire.