Cyclospora outbreak in the US drives searches and sparks health alert

The topic “cyclospora” registered a significant increase in online searches following an unprecedented outbreak of infections in the United States. More than 15,000 confirmed cases have been reported in 47 states and the District of Columbia since May, far exceeding the previous year's figures, which recorded around 1,180 cases between May and August of last year.

What is cyclospora and its symptoms

Cyclosporiasis is a parasitic infection caused by the parasite Cyclospora cayetanensis, known simply as cyclospora. It is usually contracted through contaminated food or water and causes gastrointestinal symptoms often associated with food poisoning, such as diarrhea, nausea, and vomiting.

The most common symptom is watery, frequent, and sometimes “explosive” diarrhea, which can come and go. Other issues include fatigue, loss of appetite, weight loss, bloating, gas, stomach cramps, muscle aches, and a low-grade fever. While unpleasant, the illness is not generally known to cause death, and in many cases, people recover at home without visiting a doctor. However, it can cause more serious complications in people with compromised immune systems or other underlying health conditions. If left untreated, cyclosporiasis can persist for a month or longer. Treatment may include antibiotics, anti-diarrheal medications, and hydration. Health experts encourage those experiencing symptoms, especially diarrhea lasting more than one or two weeks, to seek medical attention.

The scale of the current outbreak in the United States

Since May 1, 15,716 cyclospora infections have been confirmed in 47 states and Washington, D.C., according to an update from the Centers for Disease Control and Prevention (CDC) on August 18. This number represents an increase of 1,821 cases since the previous report on August 11. Although confirmed cases are still rising, the overall upward trend is declining, with previous weeks recording increases in the range of 2,000 to 3,000 cases.

In addition to the confirmed cases, there are at least 11,841 additional cases that have not yet been laboratory-confirmed. The CDC only reports laboratory-confirmed cases that occurred on or after May 1 in people who did not travel internationally in the 14 days before their illness began. There is a lag of about six weeks between illness onset and the case being reported to the CDC. A Nexstar analysis of health data across several states indicates more than 30,000 confirmed or probable cyclosporiasis cases nationwide this year, including those acquired domestically and internationally, and, in some states, tests that have not yet been laboratory-confirmed.

Michigan and Ohio remain the two hardest-hit states. Michigan, which has been the center of the largest cluster of cases, recorded 14,277 total cases by August 20, up from 13,909 on August 11. Only three states—Delaware, Hawaii, and New Mexico—have no federally confirmed cases. There have been two deaths and 828 hospitalizations associated with the outbreak.

Origin of the main outbreak sources

The CDC is investigating multiple separate clusters of the gastrointestinal illness, but only one source has been identified so far. It is unlikely that there is a common cause behind all outbreaks nationwide. The largest outbreak, concentrated in Michigan, was traced by the Food and Drug Administration (FDA) to recalled iceberg lettuce grown by produce giant Taylor Farms in central Mexico.

This specific cluster of illnesses, initially identified through tracing at the fast-food chain Taco Bell, was responsible for 9,481 cases and 398 hospitalizations across 17 states by August 13, according to the CDC. Maine and Massachusetts were added to that count late last week. Both deaths that occurred in the outbreak were associated with the lettuce-linked outbreak, though Michigan health officials cautioned that the two individuals who died had “significant underlying health conditions.”

In addition to the lettuce outbreak, the FDA is investigating seven other active cyclospora outbreaks with no identified source. Three of them have been closed, affecting 18, eight, and two people, respectively. Two outbreaks have grown: one, first reported in early August, reached 11 cases, and another, from late July, rose to 172 cases from a previous 115.

Challenges in investigation and prevention

Tracing the source of a cyclosporiasis outbreak is more difficult than other foodborne illnesses due to a long incubation period, difficulty in obtaining samples, and the inability to use the same genetic tracing tools available for pathogens like E. coli and listeria. Investigations can take “a significant amount of time” to determine the cause. Furthermore, the actual number of people who became ill this summer is likely higher than the counts reported by the CDC and state authorities, as not everyone infected shows symptoms, requires hospitalization, or undergoes testing to confirm the diagnosis. Symptoms can also take weeks to manifest.

The Michigan health department had reported on August 6 that the pace of new case reports and emergency room visits was slowing, and that residents could resume their normal lettuce consumption habits. However, some experts suggested caution. Dr. Sharon Nachman, chief of the Division of Pediatric Infectious Diseases at Stony Brook Children’s Hospital, stated that “it is not unreasonable to continue washing your lettuce at this point while we watch the numbers come down.”

With information from USA Today, The Hill.