Authorities are struggling to get the outbreak of an explosive diarrhea-causing parasite under control. According to the Centers for Disease Control and Prevention, there are more than 18,000 cases that have been confirmed or are being investigated across 45 states.

There had been 423 reported hospitalizations, but at least no deaths — until this week. On Monday, Michigan health officials confirmed that there are now two fatalities linked to the outbreak, an intestinal illness called cyclosporiasis which is caused by the microscopic parasite Cyclospora cayetanensis.

However, it’s important to note that both individuals had “significant underlying health conditions that may have been impacted by cyclosporiasis and dehydration,” according to an update by Michigan Health and Human Services. In other words, both people didn’t die purely because they were infected by the parasite.

Cyclosporiasis is a gastrointestinal illness that causes watery and frequent diarrhea. There are specific treatments available for the infection, including sulfonamides, which are synthetic antimicrobial agents.

The vast majority of people recover after a few days, weeks, or even a month in severe cases. But in combination with a slew of pre-existing conditions, the illness can prove fatal, as the latest news highlights.

Michigan has been hit particularly hard, representing the majority of cases being tracked, with 11,234 reports and almost 200 hospitalizations. Fortunately, the numbers are starting to wane — though it’s far too early to tell if the state is out of the woods just yet.

“We have growing confidence that the outbreak is declining,” Michigan health department spokeswoman Michigan’s health department told the New York Times.

The Food and Drug Administration has honed in on iceberg lettuce that was supplied by Taylor Farms, a company that has made significant donations to the Trump administration and is has been linked to the use of prison labor.

Despite plenty of evidence to the contrary, White House officials declared the outbreak “under control” on July 21. Cases of the illness have risen more than tenfold since then.

More on the outbreak: Almost the Entire Country Is Drowning in Cases of Explosive Diarrhea