Key facts
- An outbreak of cyclosporiasis has infected nearly 7,000 people across 34 US states.
- The parasitic infection causes frequent, watery, and explosive diarrhea.
- No deaths have been reported, but 141 patients have been hospitalized.
- The source of the outbreak remains unidentified, though past outbreaks have been linked to raw produce.
- Michigan and Ohio are among the hardest-hit states, with thousands of reported cases.
Nearly 7,000 people in the US may have a diarrhea-causing parasite, the Centers for Disease Control and Prevention (CDC) has said. Cyclosporiasis is an infection caused by a microscopic parasite, with the main symptom being frequent, watery and explosive diarrhea. People can become infected by consuming food or water that contains the parasite. The outbreak has now spread to 34 states. Michigan and Ohio have been hit particularly hard, with the two states reporting more than 3,000 cases on Friday. More than 1,000 of those cases were diagnosed over the previous two weeks. No deaths from the recent infections have been reported in the US. While the source has not yet been identified, past outbreaks have been linked to raw produce. According to the CDC, more than 400 cases are linked in four Midwestern states: Michigan, Ohio, West Virginia and Kentucky. Michigan has reported 3,309 illnesses across the state since July 9. New York has reported 510 cases, with more than half coming from New York City alone. Ohio has reported more than 400 cases in the past month. North Carolina has reported 307 people have been sickened, with 13 cases requiring hospital admissions. Illinois has reported 194 probable cases, calling it a "higher-than-average" figure for this time of year. Other states with a large number of cases include Indiana, Texas and New Jersey, according to the CDC. The number of people sick with cyclosporiasis is likely higher than the number reported because some people recover without medical care and are not tested for the illness. The CDC said it anticipates the case counts will continue to rise as new data comes in. Cyclosporiasis is an intestinal illness caused by a microscopic parasite, according to the CDC. People can become infected by consuming food or water that contains the parasite. The illness is not usually life threatening, according to the CDC, and is less common than other foodborne illnesses such as salmonella and E. coli. People who are infected with cyclospora may or may not experience symptoms. The illness usually causes diarrhea "with frequent and sometimes explosive bowel movements", says the public health agency. If untreated, the illness may last from a few days to over a month, and symptoms may return after appearing to dissipate. It usually takes about one week after infection to become sick. Person-to-person transmission does not occur, according to Dr Caitlin Rivers, of the Johns Hopkins Center for Health Security. The epidemiologist wrote in an July 8 newsletter that transmission was exclusively faecal-oral via ingestion of contaminated food or water. Those who were infected "became sick after eating food in the United States", the CDC said, and did not report any travel during the 14 days before they got sick. No specific type of produce or any grower or supplier has been identified as the source. "Contamination typically occurs at the farm or irrigation level, making traceback investigations difficult," Rivers wrote. Previous cyclospora outbreaks in the US and Canada have been linked to bagged salad mixes and kits, fresh cilantro, fresh basil, raspberries, snow peas and green onions. Given the large and increasing number of cases, Michigan's health department has recommended restaurants and kitchens preparing or serving raw produce reduce risk by thoroughly washing greens, cooking raspberries and leafy greens when possible, and removing outer layers of lettuce and green onions. While the US Food and Drug Administration says rinsing produce is unlikely to be effective, the CDC still recommends it. People who are experiencing diarrhoea are urged to contact a health provider and ask about possible infection, officials said.