Outbreak of explosive diarrhea that sickened at least 500 linked to parasite in bagged salad

An outbreak of explosive diarrhea that sickened at least 500 people in Florida was caused by bagged salad.

Investigators at the Centers for Disease Control and Prevention (CDC) linked the cluster of illnesses from last year to bags of salad contaminated with a parasite known as cyclosporiasi.

Many cases were linked to one specific brand of Caesar salad containing only romaine lettuce sold by a specific grocery store chain, but neither were named. 

Often found in feces, the micro-organism is spread onto food by contaminated water — which then sparks an infection when it is ingested by humans.

Patients with the disease suffer from watery diarrhea, a loss of appetite, cramping, bloating and feelings of nausea. The sickness can last for more than a month, although most cases resolve within a few days.

Shown above is the parasite cyclosporiasis at different stages of its life cycle. At the top, it is shown in its immature form. At the bottom left, a ruptured parasite is shown that has released two younger cyclosporiasis and at the bottom right it is shown when it is able to cause infection in humans

The CDC revealed the cause of the sickness outbreak that occurred last year in a report published yesterday. 

The Florida Department of Health surveyed 457 out of the 513 cases reported in order to investigate the source.

They found that 200 patients had eaten a prewashed bagged salad, with 85 of them having consumed the same brand of Caesar salad from the same grocery store chain that contained only Romaine lettuce.

An international link was ruled out when it emerged that 330 of the patients had not traveled internationally before getting sick in the spring and summer of 2022.

Investigators were unable to discover at which farm the salad leaves had become contaminated.

But in the past outbreaks have been caused when cattle are allowed to graze near fields growing lettuces.

Their feces, along with the parasite, then get into the water supply which is sprayed onto the lettuce — spreading the pathogen and causing illness.

The disease-causing pathogen can then contaminate plants from other farms at factories when these are mixed together as the salad is prepared. It can also get onto machinery, spreading the illness further.

To avoid the illness, the CDC recommends washing all fresh produce before eating it or cooking with it.

They also say that an opened bag of refrigerated leafy greens should be consumed within two days.