University of Wisconsin–Madison Medical College of Wisconsin

COVID-19 Outbreak Associated With Ice Fishing

Blaise Vitale, MD, FAAFP

WMJ. 2021;120(1):5.

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Ice fishing is a popular pastime in northern Wisconsin and Minnesota. Makeshift villages show up on area lakes every winter and remain there most of the winter. Wisconsin mandates that ice houses must be removed from lakes by March 15. This may be the first documented outbreak of COVID-19 associated with ice fishing.

During my regular clinic on Friday, January 29, I was assigned to do COVID testing. Our small clinic at a critical access hospital allows asymptomatic people to be tested by laboratory personnel, but symptomatic people are supposed to be seen by a provider. The first 2 patients were a couple in their 30s. They requested testing after finding out the previous day that someone with whom they had been ice fishing on a lake in northern Polk County, Wisconsin, during a family outing on January 23 had tested positive. Both patients had started to develop mild upper respiratory symptoms on January 27. Rapid antigen testing (Quidel) was positive for both patients. The family then brought multiple other members to our clinic over the course of the day and 9/9 tests were positive.

The patients ranged in age from 4 to 67 years. No one reported sharing beverages, but several meals were consumed and they used 3 ice houses. In total, 11 people were affected, including the presumed index case who was tested early in the week with a polymerase chain reaction (PCR) test at another clinic. Three patients were pediatric (2 of whom were asymptomatic). Subsequently, all 9 positive rapid antigen tests were confirmed positive by a send-out PCR test. Further, genetic analyses indicated that 8 samples shared very similar sequences (0-2 mutations apart), suggesting a common source and/or direct transmission (4 had identical sequences).

When I saw the 67-year-old family member, I alerted her to the availability of administering monoclonal antibodies to mitigate the risk for severe disease. Her 69-year-old husband had tested positive at a drive-through site in Polk County, Wisconsin on January 28 but was not notified about the availability of treatment. He then came into the office and was evaluated as well. He did have a symptomatic hypertrophic cardiomyopathy but was otherwise healthy. After receiving an exam, being provided with the appropriate educational material, and a discussion of risks and benefits, the 67-year-old patient and her husband received infusions of bamlanivamab on the same day.

The 69-year-old husband reported some low-grade fevers and chest pain overnight, such that he presented to our emergency department the following day. Because of an abnormal electrocardiogram and a mildly elevated troponin, he was transferred to the Twin Cities (Minneapolis/St Paul, Minnesota) for evaluation but was discharged after an overnight period of observation without any intervention. The 67-year-old female patient had complete resolution of her symptoms within 2 days.

While preparing this report, our clinic subsequently found a second outbreak associated with ice fishing on a Burnett County, Wisconsin lake.

These may be the first reported outbreaks of COVID-19 associated with ice fishing. As demonstrated by these cases, while ice fishing is usually thought of as a safe outdoor activity, fishing within the more comfortable ice houses available do represent a potential unrecognized hazard.

Author Affiliation: Burnett Medical Center, 257 W St George Ave, Grantsburg, Wis; email
Funding/Support: None declared.
Financial Disclosures: None declared.
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