CDC warns of ‘very big shift’ as cyclosporiasis cases surge

SALT LAKE CITY — The U.S. is experiencing cyclosporiasis outbreaks, with 1,645 confirmed cases and at least 5,100 suspected cases that are being analyzed, according to federal public health officials who suggest it’s likely an undercount.

While it’s not unusual to see some cases, an unusually high number are currently circulating, said Gwen Biggerstaff, deputy director of the Centers for Disease Control and Prevention’s Division of Foodborne, Waterborne and Environmental Diseases, during a media briefing Tuesday.

So far, cases have been reported in 34 states.

“This is much, much higher than what we’ve seen last year or the year before, and that’s a big part of why we wanted to have this briefing today to share our concerns and what we do know, because it is a very big shift from what we’ve seen in previous seasons,” she said.

“States are continuing to report an unusually high number of cyclosporiasis cases and in particular we are seeing a large outbreak in at least four states that likely have an epidemiologic link,” Biggerstaff said. Those states are Michigan, Kentucky, West Virginia and Ohio.

What is cyclosporiasis infection?

The intestinal infection is caused by a nasty little parasite called Cyclospora cayetanensis, the illness spread by ingesting food or water that has been contaminated with feces. It’s endemic in some tropical and subtropical areas, according to the Centers for Disease Control and Prevention. Cases here and there in the United States and elsewhere, however, are not uncommon.

Biggerstaff and Donald Prater, the Food and Drug Administration’s acting deputy commissioner for food, told reporters that most cyclosporiasis outbreaks have been linked to fresh produce that is consumed without being washed or prepared properly. So far, no particular food source has been identified, they said, although Michigan health officials have suggested lettuce as a possible source in their state.

Symptoms, which usually appear within a week or two of exposure, include “watery diarrhea, sometimes frequent, along with cramping, nausea, loss of appetite, fatigue and low-grade fever,” per Biggerstaff.

It’s important to note, per Biggerstaff, that the infection does not spread person to person. “The source of this outbreak is what we eat or drink, not casual contact with someone who’s sick.”

Prater said it’s likely cases will continue to spread through August. The typical season for cyclosporiasis is May to August.

Hunting for the source

The ongoing investigations to find infection sources show “a likely common source,” prompting the CDC to post an investigation notice about the outbreak, Biggerstaff said. “Public health officials are working right now to combine detailed epidemiologic interviews with genotyping of cyclospora from stool specimens to identify clusters of related cases alongside tracebacks conducted by state and local health departments and FDA.”

She added that tracebacks are hard, because by the time someone has symptoms and the illness is confirmed, so much time has passed that it’s hard to match a contaminated product to the outbreak strain. So they use a process called targeted genotyping, “which is useful for detection but not as fast and precise as whole-genome sequencing.” As a result, she added, cyclosporiasis investigations tend to take longer to link cases to each other and identify a specific source.

A specific source may not be identified, she warned.

Biggerstaff said the CDC sent an advisory to clinicians and public health partners nationwide encouraging specific testing for cyclosporiasis if patients have prolonged gastrointestinal illness. It also launched a new outbreak investigation webpage. The CDC plans to update the cyclosporiasis information at least once a week for a while.

Cyclospora infections are reportable in 47 states, and other states may report them on a voluntary basis, per the briefing.

The CDC surveillance map shows Utah has had between one and 10 cases since May, but the Utah Department of Health and Human Services reported July 10 that the single case of which it’s aware is not related to the ongoing national outbreak. The Utah news release also noted “our team continuously monitors data from across the state and there has not been an unusual increase in the number of people who seek care for gastrointestinal symptoms.”

The release notes that “it’s normal for Utah to see cases of this illness beginning in May.”

Tips to avoid the illness

Biggerstaff offered suggestions for keeping food safe from cyclospora contamination:

• Wash your hands and any fresh produce thoroughly under running water before eating, cutting or cooking.
• Cooking kills the parasite, so heating food to 158°F or higher is effective.
• If you develop prolonged watery diarrhea, especially lasting more than a few days, along with fatigue or loss of appetite, contact your healthcare provider and mention cyclospora specifically. Routine stool tests don’t always screen for the parasite, and you may need to specifically request testing for cyclospora, she said.
• People with symptoms should stay well hydrated and avoid preparing food for others while acutely ill out of general caution.

Prater said the FDA “has developed improved methods for cyclospora detection and attribution and has worked with domestic and international regulatory partners to share these methods. As such, we expect to see increased detection with these strengthened surveillance efforts.”

He also noted that the FDA plans to update active outbreak investigations every Wednesday.