Several swimmers at the Gränna lagoon in Sweden have reported infections from water fleas over the weekend. The municipality has confirmed the cases and is responding to the situation. Authorities attribute the infections to a proliferation of the microscopic crustaceans in the lagoon’s waters. Warning signs will be erected at the bathing area on Monday to inform visitors of the potential health risk. The municipality advises bathers to exercise caution and be aware of the possibility of infection. While typically not dangerous, water flea exposure can cause skin irritation and discomfort. Further investigation into the cause of the outbreak is underway.