Federal agencies are investigating four ongoing cyclospora outbreaks in the United States. This year has seen a record number of cases, prompting concern among consumers and experts.

In its latest update, the U.S. Centers for Disease Control and Prevention (CDC) reports 13,895 laboratory-confirmed domestic cases of the parasitic infection across 45 states since May. They are also tracking an additional 10,455 cases that have yet to be confirmed. There have been two deaths in individuals with underlying health issues.

The biggest outbreak now spans 15 states and has a confirmed case count of over 6,000 people, according to CDC. The agency is still investigating Taylor Farms iceberg lettuce as the likely source after previously declaring their testing a false positive. Taylor Farms has voluntarily recalled their products in 27 states across the U.S.

Agencies are also investigating three additional outbreaks that have already ended.

Cyclospora is a parasite that often contaminates fresh produce, infecting those who eat it. May through August is considered cyclosporiasis season in the U.S. Symptoms usually appear one week after exposure, and most commonly include watery diarrhea, nausea, and fatigue. While treatable, many cases clear up on their own, and aren’t diagnosed, says Glenn Morris, Professor of Infectious Diseases at the University of Florida College of Medicine and Founding Director of the Emerging Pathogen Institute.

“Because fresh produce items typically have short shelf lives, outbreaks of Cyclospora tend to appear suddenly, and gradually fade as the product is consumed out of the marketplace,” Craig Hedberg, a Professor at the University of Minnesota who focuses on foodborne illness and infectious disease outbreaks, tells Food Tank.

Better and more widely available diagnostic testing methods in clinical laboratories may lead to higher case counts, according to Hedberg. And when awareness of an outbreak grows, more people are likely to seek medical care.

Morris points to an additional explanation: a breakdown in the country’s food safety programs.

Read the full article about the Cyclospora outbreak by Amanda Kraus at Food Tank.