The “Explosive Diarrhea” Parasite Has Now Spread to 31 States

Here’s what we know — and how to protect yourself.

Map of Outbreak; July 12, 2026 https://www.cdc.gov/cyclosporiasis/php/surveillance/index.html

On July 10, 2026, the CDC updated its report on an outbreak of the parasite Cyclospora, which has been detected in 31 states across the United States.

What Is Cyclosporiasis?

Cyclosporiasis is an intestinal illness caused by the microscopic parasite Cyclospora cayetanensis. People can become infected by eating contaminated food or drinking contaminated water, most commonly through fresh produce. After exposure, a patient can become symptomatic anywhere from two days to two weeks later, with an average time of one week. Thankfully, transmission has not been reported from person to person.

Unlike many foodborne illnesses that spread through undercooked meat or spoiled food, Cyclospora often contaminates fruits and vegetables before they reach the grocery store. Once inside the body, the parasite infects the small intestine, leading to symptoms such as watery diarrhea, stomach cramps, bloating, nausea, fatigue, loss of appetite, and weight loss.

One unusual feature of cyclosporiasis is that symptoms can come and go in waves for weeks or even months if left untreated, making it particularly frustrating for many people and more challenging to diagnose.

A Multistate Outbreak

Since May 1, 2026, the CDC has received reports of 843 confirmed domestic cases of cyclosporiasis, 86 of which have required hospitalization, a rate of 10.2 percent. However, these are only the confirmed cases. The number may be much higher, as cyclosporiasis is not routinely tested for in parasite panels in the United States. Even if a patient is tested, false negatives are common because parasitic shedding is inconsistent, even with severe symptoms.

In the current Outbreak, the infected individuals range in age from 5 to 88, with a median age of 44. Thankfully, there have been no reported deaths as of today.

This is an alarming number, as it exceeds what would typically be expected based on known circulation patterns and is therefore classified as an outbreak. In the last two weeks, compared to the same period in 2025, the CDC has reported a significant uptick in cases.

Scientists are working to trace the cause of the Outbreak, and a singular source has not yet been identified. It is believed that the patients have been infected after eating contaminated food here in the States, as none of the patients have reported traveling outside of the country in the two weeks leading up to their symptoms.

How Cyclosporiasis Is Treated

Unlike viral stomach bugs, cyclosporiasis can usually be treated effectively with medication. The standard treatment is the antibiotic trimethoprim-sulfamethoxazole (TMP-SMX), also called Bactrim or Septra. Most adults take the medication twice a day for 7 to 10 days, and many begin feeling better within a few days of starting treatment. People with weakened immune systems, such as those living with HIV, may require longer treatment courses because the infection is more likely to return.

One challenge is that there are currently no highly effective alternatives for people who are allergic to sulfa medications, the class of drugs that includes TMP-SMX. Doctors may recommend supportive care, such as staying hydrated while symptoms run their course, or, in select cases, consider other less-proven treatment approaches.

Luckily, even without antibiotics, many otherwise healthy people eventually recover, but the illness can linger for weeks or even months and often follows a frustrating pattern in which symptoms improve, then return before finally resolving. At present, no vaccine is available to prevent cyclosporiasis.

Despite this, it is still recommended that any person who is infected receive treatment, if eligible, as dehydration can lead to complications.

How to Protect Yourself

While treatment options are available for cyclosporiasis, the best way to stay protected is to prevent infection in the first place. While there are no realistic steps that can guarantee you won’t get sick, the best course of action is to cook your food, as the parasite cannot survive temperatures above 158 degrees Fahrenheit (70 degrees Celsius).

Additionally, it is recommended that you wash all your produce with clean running water, even if you plan on peeling it. However, one unfortunate thing about this particular parasite is that some research suggests that washing your produce may not be enough, as it can be stickier than other types of parasites.

Looking Forward

The CDC and state health departments continue to investigate the Outbreak in an effort to identify the contaminated food source and prevent additional illnesses, though unfortunately, a consistent source has yet to be established.

As more patients are interviewed and laboratory testing continues, investigators may be able to link cases to a specific product or distributor, which could lead to recalls or other public health actions.

Until then, anyone who develops persistent watery diarrhea lasting more than a few days, especially after eating fresh produce, should seek medical care and mention the possibility of cyclosporiasis. From there, a medical professional will assess their specific pathology and determine if testing is required.

While this Outbreak is concerning, the good news is that the illness is treatable, and with prompt diagnosis and appropriate antibiotics, the overwhelming majority of people make a full recovery.