Cyclospora Outbreak In US: What to Know About The Parasite Behind The Rising Diarrhoea Cases

Last Updated:July 11, 2026, 22:20 IST

A diarrhoea-causing parasite has spread across 31 US states, with health officials reporting a rise in infections.

A diarrhoea-causing parasite has infected people across 31 US states, with several regions reporting a sharp rise in cases over the past two weeks compared with the same period last year, according to the US Centers for Disease Control and Prevention (CDC). While investigations are underway, health officials are yet to identify the source of the current outbreak.

What Is Cyclospora?

Cyclospora is a microscopic parasite that causes Cyclosporiasis, a gastrointestinal illness that spreads through contaminated food and water. Although the parasite has been linked to several foodborne outbreaks in the past, authorities have not yet determined what is driving the current surge in infections across the US.

Where Has the Outbreak Spread?

The outbreak has been concentrated mainly in the Midwest.

Michigan has reported the highest number of infections, with 1,562 cases recorded as of July 10, according to the state’s health department. Significant increases have also been reported in New York, Illinois and Ohio.

The CDC said that, as of July 10, it had confirmed more than 800 cases reported since May 1. In addition, over 1,500 more cases are still being analysed. The agency noted that these figures are likely an underestimate because its national data is updated more slowly than reports from state health departments. Case numbers typically rise during the spring and summer months.

Symptoms to Watch For:

• Watery diarrhoea is the most common symptom of Cyclosporiasis.

• Loss of appetite may occur after infection.

• Unexplained weight loss is another commonly reported symptom.

• Some infected individuals may not experience any symptoms despite carrying the parasite.

• Symptoms typically develop about one week after a person becomes infected.

• The infection can be treated with commonly prescribed antibiotics, including Bactrim or Septra.

• There is currently no vaccine available to prevent Cyclosporiasis.

How Does the Parasite Spread?

Cyclospora is transmitted indirectly between people. After being released into the environment, the parasite requires one to two weeks on fresh produce or in water before it becomes infectious to humans.

Once a person is infected, the parasite can spread further if contaminated hands come into contact with food. Previous outbreaks in the US have been associated with fresh produce including basil, cilantro, lettuce and raspberries.

What Precautions Are Being Recommended?

• Avoid consuming food or water that may be contaminated with feces, especially while travelling in tropical or subtropical regions, as advised by the CDC.

• Wash fruits and vegetables thoroughly before eating to help remove possible contamination.

• Discard or cut away any damaged or bruised portions of fresh produce before consumption.

• Follow proper food hygiene practices when handling fresh produce to reduce the risk of infection.

• No deaths linked to the current Cyclospora outbreak have been reported so far, according to health officials.

Investigation Into the Source Continues: The CDC and the US Food and Drug Administration (FDA) are continuing efforts to identify the source of the outbreak.

Meanwhile, Michigan’s health department has advised residents to avoid eating bagged lettuce and to wash basil, cilantro and raspberries thoroughly until more information becomes available.

Some Taco Bell franchise locations in southeastern Michigan have also temporarily stopped serving lettuce during the outbreak, according to an earlier Bloomberg report. However, no link between Taco Bell and the outbreak has been established, and the company declined to comment.

Has Disease Tracking Been Affected?

The CDC stopped monitoring Cyclosporiasis through its FoodNet surveillance system in 2025, along with five other foodborne illnesses.

FoodNet was designed to provide real-time tracking of foodborne diseases in partnership with 10 state health departments to help detect outbreaks quickly.

Although Cyclosporiasis remains a notifiable disease, meaning state health departments are still required to report confirmed cases to the CDC, the absence of FoodNet surveillance has reduced the country’s ability to monitor the outbreak in real time.

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