What Is the Explosive Diarrhoea Parasite Spreading Across the US? Cyclospora Symptoms, Treatment, and Prevention

Last updated on July 13th, 2026 at 05:18 am

With cases continuing to surface in more states, health officials from across the country are stepping up efforts to investigate an outbreak of Cyclospora, a microscopic parasite that causes severe gastrointestinal illness. Officials are still trying to determine the exact source of the contamination, but the outbreak has raised new concerns about food-borne illnesses associated with fresh fruits and vegetables. The parasite has attracted public attention after many patients reported suffering from severe watery diarrhoea often called “explosive” and other debilitating digestive symptoms that can last for weeks if untreated.

What Is Cyclospora?

Cyclospora (Cyclospora cayetanensis) is a very small parasite of the small intestine that causes an illness called cyclosporiasis. Unlike viruses that can easily pass from person to person, Cyclospora usually is spread through food or water contaminated with human waste. Past outbreaks have been associated with fresh fruits and vegetables, but investigators have not found a single food to blame for the current surge in infections. The source can be hard to trace since contaminated products are often distributed across several states before people get sick. One of the big challenges with Cyclospora is that symptoms may not appear right away, so it’s harder for patients to pinpoint exactly what they ate before they got sick.

Cyclospora Symptoms to Watch For

Most people develop symptoms about a week after becoming infected, but the incubation period can be as short as a few days and as long as almost two weeks. The common symptoms are:

• Watery diarrhoea profuse
• Abdominal cramps
• Too much gas and bloating
• Vomiting Nausea
• Tiredness
• Loss of appetite
• Weight loss, unexplained
• Fever low grade

For many food poisoning cases, it clears up in a couple of days, but Cyclospora infections can drag on for several weeks. Recovery can be especially frustrating for patients who experience a return of symptoms after a period of improvement. 

How Is Cyclospora Treated?

Cyclospora infections are usually treated with the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX). The drug is the most effective treatment for cyclosporiasis and can shorten the duration of illness significantly. Some otherwise healthy people recover without treatment, but treatment is often recommended because prolonged diarrhoea can lead to dehydration, fatigue and nutritional deficiencies. Older adults, young children, pregnant women and people with weakened immune systems are at increased risk of complications and should seek medical attention promptly if symptoms persist.

Why the Current Outbreak Is Raising Concern

Health officials have confirmed cases of Cyclospora in a number of U.S. states, and the number of reports continues to climb as more investigations are underway. But officials have yet to pinpoint a single contaminated supplier or food item as the source of the outbreak. That uncertainty makes it harder to control the spread. Food safety investigators must trace supply chains, interview patients and analyze purchasing patterns to find out where contamination happened. Since fresh food can reach supermarkets and restaurants across the country in just a few days, a single contaminated shipment can wind up in the hands of consumers in many different regions before health officials are even aware of a pattern.

How to Protect Yourself

While it is impossible to eliminate all risk, there are several precautions that can help reduce the chance of infection:

• Wash your hands well with soap and water before preparing or eating food.
• Wash fresh fruits and vegetables in running water before eating them.
• When you travel, drink clean and safe water.
• Practice good food-handling and kitchen hygiene.
• If diarrhoea persists for several days, is severe, especially after eating fresh produce or after travel, seek medical advice.

Good sanitation at all levels of the food supply chainfrom farms to restaurants also plays a critical role in preventing outbreaks. 

When Should You See a Doctor?

Persistent diarrhoea lasting longer than a few days especially when associated with dehydration, weight loss, severe stomach pain or extreme fatigue should not be ignored. Cyclospora can resemble other stomach illnesses, so laboratory testing may be necessary to confirm the infection. Doctors can begin the appropriate treatment sooner if diagnosed early, and it can help public health officials identify the source of an outbreak more quickly.

FAQs

What is Cyclospora? 

Cyclospora is a microscopic parasite that causes a diarrheal disease cyclosporiasis.

How does infection happen?

In most cases infection results from ingestion of food or water contaminated with the parasite, especially fresh produce.

What are the big symptoms?

Common symptoms include watery diarrhoea, stomach cramps, bloating, nausea, vomiting, tiredness, loss of appetite and weight loss.