Health authorities say they are closing in on the source of an outbreak of a rare food-borne illness that has hit Nebraska and Iowa with a vengeance.

The number of Nebraskans confirmed ill with cyclosporiasis has jumped to 53 since late last week, when 35 cases had been reported.  

The outbreak started in late June, and the good news is that no new onset of the infection is showing up, said Dr. Thomas Safranek, Nebraska's state epidemiologist. The most recent onset in Nebraska was late last month, he said. The numbers have risen as people are diagnosed using a test that specifies the infection.  

"It's a little bit of relief," Safranek said Tuesday. "We're able to reassure people they don't have to be concerned about picking it up at this time." 

The infection is caused by the parasite cyclospora, which authorities believe probably infected people through fresh vegetables. The illness is most commonly contracted by eating food or drinking water contaminated with human feces containing the parasite.  

Symptoms of include diarrhea, fatigue, loss of appetite, weight loss, bloating, intestinal gas, stomach cramps, nausea, vomiting, muscle aches and low-grade fever. Untreated, the illness can last two months, according to the Centers for Disease Control and Prevention.

In the United States, food-borne outbreaks of cyclosporiasis since the mid-1990s have been linked to imported produce, including raspberries, basil, snow peas and mesclun lettuce, according to the CDC. Nebraska hadn't had a case in four years. 

Consumers should wash fruits and vegetables thoroughly to reduce the risk of the illness. But there's no reason for people to modify their diets, Safranek said, because no new infections are showing up.  Food Safety News, a web site, reported Cyclospora may remain on produce even after washing.

"We think we're getting pretty close," Safranek said of efforts to identify the source of the infection.

Nebraska health officials are collaborating with those from Iowa, the Food and Drug Administration the Centers for Disease Control and Prevention.  Safranek said he thought the source would be identified in the next few days.

The only way to narrow the field of possible causes is by interviewing the victims, Safranek said, sometimes three or four times.

"We remain vigilant," he said, and the Department of Health and Human Services continues to advise doctors to test people with symptoms for the infection.

It's not easy to identify, and the disease can take weeks to resolve, he said.

"There may be people out there who are symptomatic,  and it would behoove them to be evaluated by a doctor."

The investigation continues in Nebraska and Iowa, where 81 cases have been reported. Other cases have now been reported in Kansas, Texas, Wisconsin and Illinois, Safranek said.

Of the 53 cases in Nebraska, 36 were in Douglas County and three in Lancaster County, said Leah Bucco-White, spokeswoman for the Nebraska Department of Health and Human Services. The victims range in age from 25 to 89, and three people were treated in hospitals, she said.

Other cases and where they were reported: Three Rivers Public Health Department (Dodge, Saunders, Washington counties), four; Sarpy/Cass Department of Health and Wellness, five; North Central District Health Department (Antelope, Boyd, Brown, Cherry, Holt, Keya Paha, Knox, Pierce and Rock), one; Southwest Nebraska Public Health Department (Chase, Dundy, Frontier, Furnas, Hayes, Hitchcock, Perkins and Red Willow), one; East Central District Health Department (Boone, Colfax, Nance, Platte), one; Elkhorn Logan Valley Public Health Department (Burt, Cuming, Madison and Stanton counties), one; Two Rivers Public Health Department  (Buffalo, Dawson, Franklin, Gosper, Harlan, Kearney and Phelps), one.

Reach Richard Piersol at 402-473-7241 or  dpiersol@journalstar.com.