Two people have died amid the ongoing record-breaking outbreak of explosive diarrhea from the foodborne parasite Cyclospora, Michigan health officials announced Monday.

Cyclosporiasis fatalities are extremely rare, and despite the massive size of the outbreak, some experts were still surprised by the deaths. The Michigan Department of Health and Human Services on Monday said that medical records of both individuals indicated that they had “significant underlying health conditions that may have been impacted by cyclosporiasis and dehydration.”

MDHHS noted that both fell ill with the diarrheal infection before Taylor Farms recalled its shredded iceberg lettuce grown in Mexico, which has been linked to thousands of cases in at least nine states. Cyclospora is a unicellular parasite that spreads in human feces and is often transmitted via contaminated fresh produce, such as lettuces and other fruits and vegetables that have uneven surfaces for the parasite to grip. Past culprits have included fresh herbs, raspberries, green onions, and snow peas.