Illinois, Kansas, Oklahoma and Pennsylvania are now part of a multistate outbreak of the severe stomach illness, with nearly 2,000 cases now confirmed by the CDC.

Cases of cyclosporiasis have topped 11,500 in 41 states, according to data from the Centers for Disease Control and Prevention on Wednesday.

As cases of cyclosporiasis are continuing to increase across the U.S., here's what we still don't know about a multi-state outbreak.

More than 12,000 cases of cyclosporiasis have been reported across 40 states

Investigators believe additional states will help them better construct how cyclosporiasis moved through the nation's food supply.