IT STARTED WITH A RASH ON EASTER SUNDAY—A VIOLENT SPLASH OF ITCHY RED ACROSS MY HIPS AND BUTT. I applied some hydrocortisone, absentmindedly chalked it up to either holiday stress or a recent switch in laundry detergents, and surfed the very next day.

It had been raining for weeks, but the winds were offshore and the North Pacific was serving up a steady pulse of good waves. As usual, I surfed at Asilomar State Beach or in Spanish Bay, and I wasn’t alone. There were always a few other surfers in the water—sometimes as many as eight or 10.

We knew the water wasn’t clean. There were no signs posted warning of bacterial contamination, but surfers grasp the principles of urban runoff better than most. We see it firsthand. At times, we wallow in it.

This spring was one of the wettest seasons in memory. Stormwater runoff poured into the ocean around the Monterey Peninsula—a murky discharge that drained down our streets and raccoon-infested sewer pipes like 10,000 tiny waterpark flume rides carrying a host of bacteria, pathogens and dangerous metals. After a few weeks of the deluge, I figured most of the truly dangerous crap had been flushed out into the deep submarine canyons that ring our coastline. I was wrong.

I guess you have to be a surfer to understand why anyone would risk exposure to the toxic cocktail the California coastline sloughs off during and after every rain; or, for that matter, why urban runoff frustrates and angers us so much. Imagine if the community periodically pumped sewage into your bathtub, gym or church. (Of course, surfers flush their toilets the same as everyone else. Like all environmental issues, we’re in this together.)

Over the years I’d dealt with some ear infections, a sore throat and the runs. Never anything too serious. Whenever I surfed during or after a rainstorm I swabbed my ears with alcohol and took a long shower immediately afterward.

In the weeks following Easter I started getting really sick.

First it was a week of terrible stomach cramps, then a sudden 103-degree fever. When my tonsils became infected and swollen, my doctor started getting nervous. The antibiotics were ineffective. Weeks had passed and I was no better. She began to suspect a virus or worse.

She sent me to a hematologist for a comprehensive battery of blood tests. “He’s also an oncologist,” she told me. “But don’t worry about that.”

I worried. The hematologist told me my white blood cells were dropping off precipitously. Normally, our blood carries between 5,000 and 10,000 white blood cells per microliter. Over the course of the next few days I went from 2,000 to 1,400 to 400.

Something was wiping out my whites in a hurry. Without them, I had no immune system. The hematologist ordered an immediate bone marrow exam. My hematologist was prepared to become my oncologist.

A bone marrow exam is a profound experience. Basically they drive a long needle into your pelvic bone and take a sample from your very core. It’s a trip to feel the metal spike pierce your bone and suck out virgin marrow. And yeah, it hurts like hell.

Two days later, my doctor sat me down and told me they didn’t find anything. I didn’t have cancer and my white blood cell count was rebounding. He shrugged his shoulders and told me it was just “one of these things”—an unidentifiable virus. “We’ll never know what it is,” he told me truthfully. “That’s just the way these things are sometimes.”