The Centers for Disease Control and Prevention has reportedly expanded the largest known cyclosporiasis outbreak to 15 states.

The alleged expansion includes the addition of six states, according to the Washington Post, which cited three people familiar with the matter. Those states include Arkansas, Iowa, Missouri, Nebraska, New Hampshire and North Carolina, according to a fourth person familiar who spoke to the paper.

A spokesperson from Arkansas’s health department confirmed the outbreak expansion to the Guardian, saying in a statement: “Arkansas is one of the states the CDC is adding to the multi-state outbreak for cyclosporiasis.”

The Guardian has contacted the CDC and the health departments of Iowa, Missouri, Nebraska, New Hampshire and North Carolina.

As of 28 July, the CDC had recorded 6,707 laboratory-confirmed cases of cyclosporiasis, along with approximately 11,500 suspected cases awaiting confirmation. Cases have been reported in 45 states since May, although most of the suspected cases have been concentrated in Michigan and Ohio.

The disease is a form of food poisoning originating from Cyclospora cayetanensis, a microscopic parasite that causes symptoms including diarrhea, appetite loss, bloating, extreme fatigue, low-grade fever, stomach cramps, nausea and vomiting.

Cyclosporiasis spreads through the fecal-oral route, most commonly by consuming contaminated food or water. Symptoms typically begin about a week after infection, and without treatment can last anywhere from a few days to a month or longer, according to the CDC. Those with symptoms are advised to stay well hydrated.

Although the Food and Drug Administration is still investigating six cyclosporiasis outbreaks, it has identified iceberg lettuce produced by Taylor Farms de Mexico as the source of one outbreak. In response, Taylor Farms voluntarily recalled lettuce distributed to restaurants in 27 states and grocery stores in 15 states.

On 24 July, the CDC announced that the outbreak linked to iceberg lettuce had expanded to four additional states – Illinois, Kansas, Oklahoma and Pennsylvania. As of that date, illnesses associated with the outbreak had been reported in nine states: Illinois, Indiana, Kansas, Kentucky, Michigan, Ohio, Oklahoma, Pennsylvania and West Virginia.

Michigan – the state hardest hit by the outbreak, with health officials reporting 11,234 outbreak-linked cases – on Monday reported the first two US deaths linked to the disease since the outbreak began.

The CDC has warned the public to not eat recalled Taylor Farms iceberg lettuce, and to contact healthcare providers if cyclosporiasis symptoms are experienced.