Cases of the parasite-borne disease, which causes explosive diarrhea-like symptoms, continue to rise across the United States, with investigators looking for the source so far coming up empty-handed.
For years, cyclosporiasis, a stomach-churning disease caused by the Cyclospora parasite often found on produce, has been largely treated as a food safety problem. But as health officials struggle to identify the source of the growing outbreak, some experts believe the focus on food may be obscuring the bigger picture.
Cases of the massive seasonal disease reached at least 843 people in 31 states as of July 9, according to CDC numbers, and more than 1,000 when individual state-reported data are counted.
While knowledge of past outbreaks has led state and federal health officials to issue warnings about known culprits like fresh herbs and lettuce, former officials at the Department of Agriculture and Food and Drug Administration told USA TODAY that the key to the mystery may be something even more ubiquitous than the produce itself: water.
Health officials face challenges in tracing food links
As previously reported by USA TODAY, the source of cyclosporiasis outbreaks is more difficult to track than foodborne illnesses like E.coli and Listeria, because it has a longer incubation period, is harder to detect in food and environmental samples and is not amenable to the same genetic tracking tools used for other pathogens, leaving investigators with a great deal of diligence and uncertainty.
An additional challenge is what Kalmia Nile, a professor of microbial food safety at the University of Delaware, describes as a “reduced oversight structure” at the federal level.
Last year, the CDC ended a decades-old federal-state partnership that tracked foodborne illnesses, including Cyclospora. The move no longer requires authorities to report Cyclospora as well as six other pathogens to the Foodborne Disease Active Surveillance Network, known as FoodNet.
Niles said the loss of such data could hinder health officials’ ability to track cases across the country and identify trends linking them together, such as a particular type of produce or food producer. This could risk delaying the ability of authorities to identify the source of the outbreak and prevent further transmission.
“We have very little information to work with,” Neal said. “I think we’re seeing some of the effects of that now.”
Contacted by USA TODAY, the FDA said that, “Under Secretary Kennedy’s leadership, FDA is currently investigating the Cyclospora outbreak using established epidemiological, laboratory, and traceback tools in close coordination with CDC and state and local partners.”
“Protecting the nation’s food supply is a core responsibility of the FDA, and the agency has the expertise, personnel, and resources needed to detect, investigate, and respond to foodborne illness outbreaks and take regulatory action when necessary.” The CDC did not respond to USA TODAY’s request for comment July 10.
But the food may not have real origins at all
However, with all the attention focused on food, some experts say investigators are missing a big piece of the traceback puzzle.
“The role of water in the transmission of Cyclospora to humans has probably been underestimated or underrepresented and poorly understood,” Frank Yiannas, the FDA’s former deputy commissioner for food policy and response, told USA TODAY. “There have been few large outbreaks in the United States that were related to produce, but it was possible, and in some cases proven, that water served as a medium for produce contamination.”
Water can serve as a type of delivery system for pathogens to reach our produce. This is often where the contamination that causes foodborne illnesses begins: the irrigation system, the soil, and the environment in which the food is grown.
Waste, human and otherwise, ends up in waterways where it shouldn’t through things like sewage leaks, waste water overflows, failing septic systems, flooding and surface water (rivers, canals, reservoirs and streams). When that sewage-contaminated water ends up in irrigation systems used to grow food, Cyclospora remains on the produce, infecting people when eaten raw.
In an investigation conducted by Yiannas while at the FDA, the agency traced the outbreak to red cabbage grown in South Florida, where a two-year trial found that Cyclospora was “readily prevalent” in canals used by local farmers to irrigate crops.
Dr. Robert Mandrell, a microbiology researcher and former USDA official, told USA TODAY that Cyclospora is also quite resilient and is not destroyed by chlorine, the primary disinfectant used in municipal water supplies.
“It is very resistant,” he said, noting that the parasite’s hard outer shell allows it to survive in conditions that kill many other pathogens. “One would expect that when you treat water in a wastewater facility, it can withstand that chlorine.”
Flooding, sewage and waste water can be major
Exposure doesn’t just come from eating produce grown with contaminated water, said Mandrell, who said the two states with major cases, Michigan and Ohio, have recently experienced heavy rainfall and flooding.
When heavy rainfall overwhelms sewage systems or septic tanks, raw or partially treated sewage gets mixed with flood water, which then spreads into neighborhoods, farms, waterways and low-lying areas that may eventually filter into water bodies, wells or reservoirs in recreational areas. This may result in a more direct exposure than the water-to-food route.
“It may not be drinking water that is contaminated, but we don’t know that. In some cases, it may be, but exposure to flood water also has some level of sewage in it,” Mandrell said. However, we don’t know many of these things for sure, because monitoring of Cyclospora in water sources in the United States is not routine or robust.
“You need to do a big study of not only drinking water, but also the rivers and streams in our country that are fed by waste water,” he said.
Different incidents have proven that it is possible, Yiannas said. In one case, cyclosporiasis infection was detected in tap water in a residential dormitory. In another case, a child became infected while swimming in Lake Michigan and in another case, a man became infected while cleaning sewage.
Still, both said, there is much that scientists and health officials don’t know, because the nature of the parasite makes it more difficult to study than other foodborne pathogens.
Why does the parasite remain a mystery?
Scientists understand how Cyclospora makes people sick, Mandrell said, but they still don’t fully understand how it circulates in the environment before reaching people, or what environmental conditions turn it into an infectious organism through which process. It is extremely difficult to detect in environmental samples, has unique reproductive properties and a life cycle that is almost impossible to replicate in the laboratory.
In the face of such an outbreak, both Mandrell and Yiannas said U.S. public health agencies need to invest significantly more energy and resources into studying Cyclospora and its potential for water-based transmission. In fact, Yiannas said, the questionnaire the FDA uses to trace common connections between sick people to a possible outbreak source still did not include questions about water the week of July 6.
“When we’re investigating these outbreaks, we’re not asking enough questions about it,” he said. “We don’t have a lot of data, and we should have.”
The FDA and CDC did not respond to USA TODAY’s questions about water tracing.
And while Cyclospora was previously thought to be an imported food issue, that’s still the case at least to some extent, said Mandrell, who has studied the parasite extensively in Mexico, now it’s likely a domestic issue as well — even if this outbreak is linked to something imported.
“We say it’s not endemic, but I’m not so sure,” he said. “When you think about the amount of waste, like I said, that’s coming out during this outbreak, where is it going?”
Yiannas agreed, saying, “I think the parasite is now endemic in the United States and I think it would be foolish to assume… that it is a food product from other countries.”
“If we can’t solve this outbreak, I think it really calls into question the effectiveness of our public health system,” he said.
In the meantime, Mandrell said, if people in areas with high levels of flooding are concerned about water supplies they can use bottled water until things dry out.
“If you want to be proactive, you can stay away from your water if you’re concerned about it, especially if you can see outside your windows that it definitely has some contamination,” he said.
Reporting by Mary Walrath-Holdridge and Christopher Cain, USA TODAY Network, via Reuters Connect.