Complex sentence: By September 1 of that year, over 3,800 people had reported symptoms of cryptosporidiosis, a gastrointestinal illness caused by the parasite; 425 cases were confirmed after laboratory analysis, and a total of 1,374 cases were considered to have probably originated from the park.
Split into simpler sentences: By September 1 of that year, over 3,800 people had reported symptoms of cryptosporidiosis, a gastrointestinal illness caused by the parasite. After laboratory analysis, 425 cases were confirmed and a total of 1,374 probable cases were considered to have originated from the park.