Photograph by Austin Hilgenberg
Lake Minnetonka
Can you find the bathroom in this scene? (Hint: It’s not behind the trees.) The party at Big Island on July 4.
The annual boat tie-up party near Big Island on Lake Minnetonka had been a success: A threatening rainstorm proved short-lived, the temperature peaked at 85, people ate and drank, no one drowned. For most of the day, revelers hopped from boat to boat or jumped in the shoulder-high water. There were kids, grandparents, and lots of recent grads from Orono and Mound Westonka high schools.
“So how it kind of works is boats tie up on the left and the right, and there’s a walkway through the middle,” says 24-year-old Austin Hilgenberg, a regular at boat tie-ups on Lake Minnetonka. If you’re a landlubber, picture Minnesota’s floating version of a party on South Padre Island. “People walk on the backs of boats or hop in the water and swim,” Hilgenberg adds. “No one goes onshore because it’s rocky and there are No Trespassing signs. This year, the first row tied up in deeper water, so it was about 5 feet deep, up to my shoulders. My girlfriend was on my shoulders because she didn’t want to get her makeup wet.”
By the morning of July 6, the queasiness started—the first murmurs that the party hadn’t agreed with everyone’s stomach.
Did we mention the lack of bathroom facilities at these boat tie-ups?
“The only bathrooms would be the boats that have the undercarriages,” Hilgenberg explains. “Obviously, the hundreds of boats that don’t have the restrooms aren’t going to ask to share other boats’.”
By the morning of July 7, it was official: People were sick. Vomiting, diarrhea, abdominal cramps.
In true Gen Z fashion, the news spread quickly on social media, the patients sharing the gruesome details of their symptoms via various hashtags. Some had visited the doctor or even the hospital, but no one had a name for the illness.
It may seem like a scene from South Park, but public health workers take these situations seriously. Several pathogens found in some of our lakes (such as Cryptosporidium, norovirus, and E. coli) can occasionally lead to death, not to mention intense misery.
The mystery triggered an investigation by Hennepin County Public Health’s epidemiological unit and the Minnesota Department of Health’s Waterborne Diseases Unit. The case would ultimately affect 172 people, the most since a 2013 outbreak of Salmonella (associated with a food festival) produced 119 cases. It also triggered a reaction on social media: GIFs of Prince with references to “purify yourself in the waters of Lake Minnetonka.”
Minnesota’s public health system enjoys a national reputation as a first-rate scientific outfit. But exactly how do such investigations work? If you’re picturing heroes in hazmat suits . . . well, maybe shift that picture to a scientist sitting at a desk with a phone that won’t stop flashing.
Here’s how this one went down, with commentary from the pair that led the work: Erica Bagstad, Hennepin County’s epidemiology supervisor, and Trisha Robinson, MDH’s Waterborne Diseases Unit supervisor.
July 8, 9:30 am (all times approximate): The file starts with an email from a concerned mom reporting the symptoms she’s hearing from her kid and assorted friends. The county asks the mom to share its phone number with anyone experiencing symptoms.
July 8, 11:15 am: Hennepin County epidemiology staff return from a biweekly staff meeting to discover a handful of voicemails from sick people.
July 8, 11:30 am: “The phones really start to ring,” Bagstad says.
July 8, 11:45 am: Bagstad calls Robinson. “She was totally expecting my call as the MDH food-and-waterborne-illness phone number was also ringing off the hook,” Bagstad says. They compare notes and confirm that the county will take the lead, as Big Island falls within its boundaries.
July 8, afternoon: The county pulls in staff from the environmental health and emergency preparedness departments to hit the phones. MDH relies on graduate student workers.
July 8, 10 pm news: WCCO runs a story with the number for Hennepin County Epidemiology, based on a call from Hilgenberg to the station’s tip line. “I told them, hey, I was at Big Island on the 4th and I got sick. So I posted on Instagram and my friends said, ‘I’m sick too.’ All these people think they had food poisoning, but no way we were all eating the same thing.”
July 9, 8 am: Bagstad returns to the office to another 115 voicemails.
July 8–11: Umpteen TV stations and countless reporters broadcast every detail of the horror. One day, for example, a media scrum shows up at Hennepin County’s weekly beach testing. (The county tests the water at 31 beaches, recommending closures to swimming areas that exceed a threshold count for E. coli.) Community health worker Nick Fortmeyer enjoys (suffers?) a moment in the spotlight as TV cameras capture him wading into Lake Minnetonka at Excelsior Beach, filling a plastic bottle with water, and labeling it. A cameraman directs him to repeat the process to stretch out the moment as long as possible.
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One benefit of all the attention? An unusual inflow of reports from the public. More often, Hennepin County or MDH tracks down people who’ve become ill and initiates the calls. Or people will go to their health care provider with symptoms and test positive for something that the provider is required to report to MDH.
“This time we had people who really wanted to talk to us,” Bagstad says. Consider it a manifestation of Minnesota’s neighborly ways. “I think people who were out there were so concerned and wanted to help others not get sick.”
The concern, however, appeared to have a limit: Of six stool kits sent out, only one was returned. Unfortunately, it didn’t solve the mystery, as it tested negative for the 22 common diseases that the MDH lab looks for, including the microscopic parasite called Cryptosporidium, or crypto, which is Minnesota’s most common source of waterborne disease. Others who visited their primary care providers found similar results. For example, Hilgenberg’s blood and stool samples tested negative for everything.
The beach testing didn’t help here: Big Island doesn’t have a public beach. And testing the water retroactively doesn’t work anyway, experts say. The water disperses germs too quickly.
The state investigates about 5–10 cases of suspected waterborne illnesses each year. Minnesota is extra aggressive in pursuing these cases, Robinson says. (Ironically, that makes it look like we’re extra sick here. In fact, we just investigate more illnesses than other states.) Just two people calling in similar symptoms from two different households will trigger an investigation.
Big Island marked the first waterborne investigation by Hennepin County this year, but crypto becomes more common as summer wears on. (And despite the chlorine treatment, swimmers are more likely to get sick from a pool than a lake.)
Ultimately, the Big Island case will go down in lake lore with no clear culprit. When outbreaks occur in pools, health officials can say with certainty that an ill swimmer was the cause—with the pathogen often “transmitted by the fecal–oral route,” as the Centers for Disease Control and Prevention word it. On a lake, it’s murkier. Someone might have dumped a marine toilet or been ill while swimming.
The final outbreak report hadn’t been released at press time. But Bagstad says that a few clues—the incubation period, symptoms, and the duration of the illness—point to a possible viral cause.
Though the ambiguity may not play well for the media story line, the lack of a definitive answer isn’t all that unusual.
“It was a nice-to-have, not a have-to-have,” Robinson says. Figuring it out could help some patients seek treatment and publicize a prevention message to others.
As it is, ideas to stave off future outbreaks run the gamut.
Hilgenberg is toying with bringing to the city council an idea he got from a similar lake-party event in Iowa. “Basically, it’d be a barge with two dumpsters and three restrooms. You could also have a medical tent and then also showers and lifeguards.”
Bagstad suggests something less elaborate: “Maybe simple signage that says, ‘Don’t go to the bathroom in the water.’”
It might work.
