(Changes dateline and updates numbers of cases in paragraph 1,

10)

July 30 (Reuters) - The U.S. Food and Drug Administration,

Centers for Disease Control and Prevention and dozens of states

are investigating a surge in cases of cyclosporiasis intestinal

illness. Michigan has now reported more than 10,000 cases and is

searching for links beyond the initial cases tied to lettuce.

The outbreak, one of the largest U.S. cyclosporiasis

outbreaks in recent years, has been linked to shredded iceberg

lettuce served at Yum Brands' ( YUM ) Taco Bell restaurants in

nine states. Investigations are continuing into other sources.

Here is what we know of the intestinal illness and the

outbreak so far:

WHAT IS IT?

Cyclosporiasis is an intestinal infection that can be

contracted by consuming food - typically raw fruits and

vegetables - or water contaminated with feces that transmit the

cyclospora parasite, according to the CDC.

Symptoms can range from mild to severe, with children, older

adults and people with weakened immune systems facing a higher

risk of serious illness.

While cyclosporiasis is not fatal, untreated infections can

persist for weeks and may lead to hospitalization, particularly

because of dehydration.

The United States has seen previous cyclospora outbreaks

linked to fresh produce, including a 2020 multistate outbreak

associated with bagged salads that sickened nearly 700 people in

13 states.

The U.S. Centers for Disease Control and Prevention

considers May 1 to August 31 the annual cyclosporiasis season.

The CDC has reported 6,707 laboratory-confirmed cases of

cyclosporiasis across 45 states and 423 of those patients had

been hospitalized. It expects thousands more because it can take

six weeks to determine if a sick person is part of the outbreak.

WHAT DO WE KNOW ABOUT THE CONTAMINATED PRODUCE?

The U.S. Food and Drug Administration's traceback

investigation has found a link between thousands of cases and

iceberg lettuce sold in Taco Bell restaurants in nine states

including Indiana, Kentucky, Michigan, Ohio, West Virginia,

Illinois, Kansas, Oklahoma, and Pennsylvania.

The agency initially reported on July 18 that a sample of

shredded iceberg lettuce supplied by Taylor Farms had tested

positive for the parasite, but withdrew the finding a day later

after a laboratory review determined the result was a false

positive.

The FDA investigations still point clearly to Taylor Farms,

which recalled its lettuce from central Mexico and shut down its

processing plant there. The recall included Marketside-branded

product from Walmart ( WMT ) and dozens of products distributed through

Sysco and other companies, according to the FDA.

Taylor Farms said in a July 24 statement that the recall was

voluntary and that it has "best-in-class" cyclospora prevention

protocols. It is no longer sourcing any iceberg lettuce from the

region, it said.

WHAT CAN PEOPLE DO TO PROTECT THEMSELVES?

The FDA said cooking produce to at least 158 degrees

Farenheit (70 degrees Celsius) is the most effective way to kill

cyclospora, as the parasite is resistant to routine chemical

disinfection.

The agency also advises consumers to discard the outer

leaves of leafy vegetables and thoroughly rinse fruits and

vegetables before peeling or eating them.

Cyclospora typically spreads through contaminated food or

water and is not commonly transmitted from person to person.

Past outbreaks were linked to bagged salad mixes and kits,

fresh cilantro and basil, raspberries, snow peas and green

onions.

For people who have cyclosporiasis, the CDC recommends

treatment with trimethoprim-sulfamethoxazole, an antibiotic

commonly sold as Bactrim, taken twice daily for seven to 10

days. People living with HIV may require longer treatment,

according to the agency.

WHAT SURVEILLANCE IS BEING DONE?

Cyclospora is a nationally notifiable pathogen and most

states collect robust data and share that routinely with the CDC

in its disease surveillance system, said Gwen Biggerstaff,

deputy director of the CDC's Division of Foodborne, Waterborne

and Environmental Diseases.

Healthcare providers are legally required to report cases of

cyclosporiasis to public health departments in 47 states.

The Foodborne Diseases Active Surveillance Network, or

FoodNet, is a collaboration among the CDC, the U.S. Department

of Agriculture, the FDA and 10 state health departments. Last

July, it stopped tracking six of eight pathogens, including

cyclospora, due to funding cuts.

The goal of FoodNet is to look at trends over time and the

network does not replace national surveillance, Biggerstaff

said. Participating states continue to report cyclospora on a

national basis and the data is the same for this outbreak as

with previous ones, she said.