Cyclospora outbreak expands to nine US states, health officials say

Cyclospora linked to iceberg lettuce has spread to nine US states, part of the largest reported outbreak in US history, health officials said on Friday.

Cases tied to the lettuce from central Mexico now have been reported in Illinois, Kansas, Oklahoma and Pennsylvania, according to the Center for Disease Control and Prevention (CDC). Indiana, Kentucky, Michigan, Ohio and West Virginia had also reported cases linked to the lettuce.

The cyclospora parasite causes cyclosporiasis and leads to explosive diarrhoea. There are multiple outbreaks in the US, likely from different sources.

Since mid-May, the number of cases tracked by the CDC has increased to more than 11,000 across 41 states.

Michigan has been the hardest hit state, with health officials there saying on Friday that the number infected has increased to more than 8,100.

Residents stricken by the parasite told the BBC it was "the most painful thing I've ever been through in my life".

In its update on Friday, the CDC warned people not to eat recalled iceberg lettuce from Taylor Farms that sourced from central Mexico.

Taylor Farms, a major US food supplier, voluntarily recalled all of its iceberg lettuce sourced from central Mexico on 17 July. The company said it did so "out of an abundance of caution".

Investigators from the Food and Drug Administration announced over the weekend that iceberg lettuce from Taylor Farms had tested positive for cyclospora but later retracted that statement saying it was a false positive.

Health experts that spoke to the BBC said it is often difficult to track the origins of cyclospora, the parasite that when consumed causes the intestinal illness cyclosporiasis.

Part of the challenge, experts said, is that symptoms might not appear until weeks after the parasite has been ingested, making it difficult for investigators to trace what someone has eaten and find a common link.

The investigation of the multistate outbreak tied to iceberg lettuce is expected to be slow-going, Wade Syers, a food safety and security expert at Michigan State University, told the BBC.

"For Cyclospora, it's not unusual for the picture to become clearer a couple of months after the first illnesses occur," he said in an email on Friday.

"Because these investigations are unfortunately more likely to be marathon investigations rather than a quick sprint."