Almost 1,000 people in the United States have contracted infections from  Cyclospora parasites since May 1. Health officials are baffled, saying they haven’t been able to discover the source of the microscopic creatures, which infect humans via contaminated food and/or water.

There were 988 laboratory-confirmed victims in the ongoing outbreak, spread across 40 states, as of Sept. 13. That’s a 380 percent increase in victims compared to the Aug. 2 outbreak announcement by the Centers for Disease Control and Prevention.

At that time the agency reported 206 people in 27 states had been confirmed with cyclosporiasis caused by the Cyclospora cayetanensis parasite.

Before its over, the outbreak is likely to exceed 1,000 victims. Illnesses that began after Aug. 2 may not yet have been reported to CDC because of the lag time between a victim’s first doctor visit, lab tests, paperwork and finally reports being filed with public health agencies.

The most recent update from CDC did not include information about the number of victims who have been hospitalized or whether any have died. In its Aug. 7 alert, the agency reported 18 people had required hospitalization. No deaths had been reported at that point.

“At this time, no specific vehicle of interest has been identified, and investigations to identify a potential source, or sources, of infection are ongoing. It is too early to say whether cases of Cyclospora infection in different states are related to each other or to the same food item(s),” the CDC reported Sept. 15.

Previous U.S. outbreaks of cyclosporiasis have been linked to various types of imported fresh produce, e.g., basil, cilantro, mesclun lettuce, raspberries, snow peas. Consumers should continue to enjoy the health benefits of eating fresh fruits and vegetables as part of a well-balanced diet.”

However, the CDC outbreak update again urged consumers, retailers and foodservice providers to follow safe produce handling recommendations.

2017 more than tops the charts
It’s not unusual to see an increase in Cyclospora infections in the United States between May and August or September, according to the CDC. In some previous years, outbreaks in that time frame have coincided with the availability of particular fresh produce commodities, such as cilantro from Mexico.

“Cyclosporiasis occurs in many countries but is more common in tropical and sub-tropical regions,” the CDC reported.

“To date, no commercially frozen or canned produce has been implicated (in the 2017 outbreak).”

The number of lab-confirmed cases this year is literally off the chart, though. Since the year 2000, the only annual Cyclospora case count that comes close to the numbers this year was 2005 when a March-May outbreak in Florida hit 582 people. The source was found to be basil from Peru.

In the past decade, 2007 was the only year when the CDC did not receive reports of Cyclospora parasite infections. Since then, there have been outbreaks every year.

See the chart below for the CDC’s Cyclospora counts for the past decade. Click here to see the full chart, which included outbreak data from 2000 to 2015. The numbers for 2016 are not included in the chart, but as of Aug. 3, 2016, the CDC reported there had been 88 Cyclospora infections reported in the United States that began on or after May 1, 2016.

Advice to consumers
The single-celled parasite causes intestinal infections in human beings who eat or drink contaminated food or beverages. It cannot be passed from person-to-person, according to the CDC.

It can, however, take up to two weeks for symptoms to develop. Anyone who has symptoms of cyclosporiasis is urged to seek medical attention.

Symptoms include watery diarrhea that can be profuse, anorexia, fatigue, weight loss, nausea, flatulence, abdominal cramping, myalgia, vomiting and low-grade fever.

If untreated, the illness may last for a few days to a month or longer, and may have a remitting-relapsing course. The treatment of choice for cyclosporiasis is trimethoprim/sulfamethoxazole (TMP/SMX), according to the CDC.

Year(s)* Month(s)* Jurisdiction(s)* No. of cases† Food vehicle and source,
if identified‡
2008 March Wisconsin 4 Sugar snap peas (likely) ⁂
2008 July California 45 Raspberries and/or blackberries (likely)
2009 June District of Columbia 34
2011 June Florida 12
2011 July Georgia 100
2012 June–July Texas 16
2013** June Iowa and Nebraska 161 Bagged salad mix from Mexico
2013** June–July Texas 38 Cilantro from Mexico
2013 July Wisconsin 8 Berry salad (suspected)
2014 June Michigan 14
2014†† June–July Texas 26 Cilantro from Mexico
2014 July South Carolina 13
2015 May–July Georgia, Texas, and Wisconsin 90 Cilantro from Mexico

Key to chart:
* The entries in the first three columns refer to the known or likely year(s), month(s), and
jurisdiction(s) in which the exposure(s) to Cyclospora occurred. † The case counts include laboratory-confirmed and probable cases of cyclosporiasis. By definition, each outbreak included at least two linked cases, at least one of which was laboratory confirmed. ‡ A food vehicle is specified only if a single ingredient or commodity was identified in an outbreak investigation. Click here to view the full chart covering 2000 through 2015.

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