A diarrhoea-causing parasite is spreading across the United States, infecting at least 145 people aged between five and 86 and hospitalising more than 20 of them, according to data from the US Centres for Disease Control and Prevention. The cases were recorded between May 1 and June 16, though health officials warn the true figure is almost certainly far higher.
What Is Cyclospora and How Is It Spreading?
The culprit is a microscopic parasite called Cyclospora, which typically enters the body through the consumption of food or water contaminated with faecal matter. What makes this outbreak particularly concerning is that none of the infected individuals had recently travelled outside the United States — a factor that often explains how the parasite is introduced to new populations.
Health officials believe the infections are being transmitted through contaminated food, though no specific food source has yet been identified as the vehicle of transmission. The investigation remains ongoing.
Cyclospora is classified as a "nationally notifiable disease" in the US, meaning every confirmed case must be reported to government health authorities — a requirement that helps ensure the outbreak is being closely tracked even as case numbers climb.
Which States Are Affected?
New York has recorded the highest number of infections, with between 31 and 80 confirmed cases — the majority of those reported nationally up to mid-June. However, cases have been identified across a wide swath of the country, including:
- Alaska, Colorado, Connecticut, Florida and Georgia
- Illinois, Louisiana, Massachusetts and New Jersey
- North Carolina, Ohio, Pennsylvania, Tennessee and Texas
- Virginia and Wisconsin
Michigan has emerged as a particular flashpoint, with health officials in that state investigating what they are describing as a "sudden and large" increase in cases. It is understood that more than 170 cases have now been recorded in Michigan alone — a dramatic surge given that the state typically identifies just 50 cases across an entire year.
"Michigan typically identifies 50 cases a year," a spokesperson for the Michigan Health Department said, underscoring the scale of the current spike.
Symptoms: What to Watch For
Symptoms of a Cyclospora infection generally appear roughly one week after exposure. The most common and distinctive sign is watery diarrhoea with frequent and sometimes explosive bowel movements, according to the CDC. Other symptoms include:
- Nausea and loss of appetite
- Weight loss, cramping and bloating
- Increased gas and fatigue
Less commonly, those infected may also experience vomiting, body aches, headaches, fever and flu-like symptoms. The duration of illness can vary significantly — symptoms may resolve within a few days, or persist for more than a month in some cases.
So far, no deaths have been reported in connection with the outbreak, and the 20 hospitalisations, while serious, represent a small proportion of total confirmed cases.
How Significant Is This Outbreak?
While the scale of infections across multiple states has raised alarm, health authorities note that the US typically records several hundred Cyclospora cases per year, meaning the parasite is not entirely new to the country's disease landscape. What sets this outbreak apart is the speed and geographic spread of transmission, as well as the concentration of cases in states like Michigan and New York in a compressed timeframe.
Unreleased data suggests the confirmed case count of 145 is a significant underestimate, as many infections go undiagnosed or unreported. Authorities are urging anyone experiencing prolonged gastrointestinal symptoms to seek medical attention and report their illness to health officials.
