A Cyclospora outbreak in the US has caused nearly 5,000 cases, with Michigan reporting the highest number of infections.
Health officials are investigating fresh produce, including lettuce and salad greens, as possible sources of contamination.
Experts advise safe food handling, proper washing and hygiene practices while continuing to eat fruits and vegetables.
A Cyclospora outbreak that has sickened nearly 5,000 people across the United States is under investigation, with health officials still unable to identify the exact source of contamination even as fresh produce remains a possible link. Michigan has reported the highest number of cases, while authorities are advising consumers to follow food safety measures and continue eating fruits and vegetables unless specific recalls or public health advisories are issued.
The outbreak has been reported in more than 30 states and has become the largest reported Cyclospora outbreak in Michigan, with more than 3,300 cases recorded since late May. It is also among the largest Cyclospora outbreaks reported in the US in recent years. No deaths have been reported, and health experts say infections are generally treatable with antibiotics and rarely lead to serious complications.
Cyclospora cayetanensis is a microscopic parasite that causes an intestinal illness known as cyclosporiasis. According to the US Food and Drug Administration, the parasite is so small that it can only be seen under a microscope. The US Centers for Disease Control and Prevention describes the infection as causing watery diarrhoea “with frequent and sometimes explosive bowel movements”.
The parasite is transmitted through the faecal-oral route, mainly when people consume food or water contaminated with human faeces. Fresh produce including lettuce, spinach, cilantro, basil, berries and other raw vegetables have been linked to previous outbreaks.
Health officials have not confirmed what is causing the current outbreak. In Michigan, early information has pointed towards lettuce or salad greens as a possible source, but investigations are continuing.
Tracing Cyclospora outbreaks can be difficult because contaminated ingredients may be used in multiple foods and distributed across different locations. A single ingredient such as basil or cilantro may be present in several recipes, making it difficult for investigators to determine what affected people had in common.
Previous outbreaks have been linked to raspberries, basil, cilantro, snow peas and salad mixes. Produce can become contaminated when exposed to water containing human faeces, including through unsafe irrigation practices. Contaminated food can also move through supply chains, with distributors sending the same produce to restaurants and grocery stores, making investigations more complicated.
Cyclospora outbreaks usually occur more often in late spring and summer. The heat-loving parasite requires time outside the body before it becomes infectious. Unlike many other intestinal infections, it is not usually spread directly from person to person.
The outbreak has raised questions about whether consumers should avoid raw vegetables. Experts have said there is no recommendation for the general public to stop eating lettuce or other leafy greens unless a specific food recall or public health advisory is announced.
Taco Bell said it had “voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure,” amid speculation that some vegetables used by the fast food chain could have been linked to the outbreak.
Dr. Nasiruddin G, Consultant in Internal Medicine at Fortis Hospital Cunningham Road, Bengaluru, said consumers should continue eating fresh produce while maintaining proper hygiene.
“The health benefits of eating fresh vegetables far outweigh the risk. Consumers should, however, purchase produce from reputable sources and practice good food hygiene,” he said.
Health experts recommend washing hands with soap and water after using the bathroom and before handling food. Alcohol-based hand sanitisers do not kill Cyclospora, but soap and water can help remove the parasite from hands.
Produce should be washed thoroughly under clean running water. When washing herbs such as cilantro and basil, leaves should be separated before cleaning. For green onions, consumers should remove the roots, take off the outer layer and rub the surface under running water.
Cooking produce to an internal temperature of 158 degrees Fahrenheit (70 degrees Celsius) or higher can kill Cyclospora. Experts also recommend peeling fruits and vegetables where possible, washing cutting boards and cleaning kitchen surfaces.
Some produce can be more difficult to clean because of its structure. Broccoli and cauliflower have tight crevices that can trap contamination, while berries have fragile surfaces that make thorough cleaning difficult. Dr. Erika Noel, an assistant professor at Hawaii’s medical school and a paediatrician on the island of Kauai, has suggested cooking berries in pies or making jam instead of eating them raw.
Melons should be scrubbed on the outside before cutting because a knife can carry germs from the rind into the fruit. Experts also recommend choosing whole lettuce heads instead of pre-mixed salads and removing the outer leaves.
For pre-mixed salads labelled as washed, experts advise washing them again with water. Research shows vinegar does not kill Cyclospora but can help remove contamination. Noel recommends soaking produce in a mixture of three parts water and one part vinegar for a few minutes before rinsing with water. A salad spinner can help remove the vinegar taste after rinsing.
However, Dr. Nasiruddin said household cleaning methods cannot guarantee complete removal of Cyclospora if produce is contaminated.
“Simply rinsing vegetables under running water helps remove dirt and may reduce some contamination, but it cannot reliably eliminate Cyclospora if the parasite is present. Household disinfectants, vinegar, salt water, or baking soda washes have not been proven to completely kill Cyclospora on fresh produce,” he explained.
Dr. Noel said the outbreak should not discourage people from eating fruits and vegetables.
“We don’t need to panic,” she said.
Cyclospora infections also occur in India, particularly because the parasite is found in tropical and subtropical regions. Dr. Nasiruddin said large foodborne outbreaks linked to commercially distributed produce are reported less frequently in India, while some cases may go undetected because routine stool microscopy may miss the parasite unless specifically looked for.
“Cyclospora infections do occur in India, particularly because the parasite is endemic in many tropical and subtropical regions. However, large foodborne outbreaks linked to commercially distributed produce are reported less frequently than in North America. Sporadic cases are likely underdiagnosed because routine stool microscopy may miss the parasite unless specifically looked for. Maintaining safe water supplies, proper sanitation, and good agricultural practices remains the cornerstone of prevention,” he said.
Health authorities continue to investigate the outbreak while urging consumers to maintain basic hygiene practices and follow safe food preparation methods.
(With inputs from AP and Livemint)
