Cases of cyclosporiasis – a parasitic illness that causes “explosive”, watery diarrhea – have grown exponentially in recent days, health officials said, with an abnormally large outbreak reported in Michigan.
Almost 700 cases were reported to the state’s health department by Monday, ABC News said, up from 170 six days earlier, and almost 14 times Michigan’s average annual caseload of 50.
On Friday, the Centers for Disease Control and Prevention (CDC) said there were more than 400 cases across 18 states, and that it was working with the US Food and Drug Administration (FDA) to investigate the “alarming” clusters.
“The true number of people sick with cyclosporiasis was likely higher than the number reported,” the CDC said in a bulletin, noting that many victims recover without seeking medical care or testing.
Although cyclosporiasis is rarely life-threatening, and no deaths have been reported from the current outbreak, the intestinal illness can have severe effects.
Symptoms include cramps, nausea, fatigue, loss of appetite, low-grade fever and vomiting. “Watery diarrhea with frequent and sometimes explosive bowel movements” is the most commonly reported symptom, according to the CDC.
Cyclosporiasis is caused by the parasite cyclospora, which spreads through raw produce and water contaminated with human feces. Previous outbreaks have been linked to fresh fruit and vegetables, including a surge of cases in Florida in 2022 caused by contaminated lettuce in packaged salad kits that sickened hundreds of people.
The average time from ingestion to symptoms appearing is about one week, but can range from two days to about two weeks, health officials said, noting that it is not usually transmitted from person to person.
In Michigan, experts predict cases will continue to rise as people become aware of publicity over the current outbreak and seek testing and treatment.
Dr Natasha Bagdasarian, Michigan’s chief medical executive, told ABC: “There is a significant lag time between exposure to contaminated produce or contaminated materials and development of symptoms.”
She added that the 678 cases reported as of Monday represented “a moving target”.
The ABC report on Monday also noted a significant rise in cases in Ohio, which numbered 177 as of 2 July, the state’s health department said, with 171 of those reported since 20 June.
While officials work to establish any link between clusters, which have emerged most visibly in the south-east of Michigan, including Detroit, there is no suggestion of a connection to outbreaks in other states, the CDC said.
According to the center’s most recent update on 1 July, cases had been reported in 17 states, and 20 people hospitalized. Summer months traditionally see a rise in cases, the CDC said, resulting in a “cyclosporiasis season” from 1 May to 31 August.
Health officials recommend cooking fresh produce where possible to reduce the risk of illness, or thoroughly washing it in clean, running water.
