CDC researchers can compare the DNA of salmonella strains

ATLANTA (CNN) -- About 100 people in at least seven states have become ill recently with an unusual form of salmonella, according to the Centers for Disease Control and Prevention.

Six people in Illinois have been hospitalized in the past two months with Salmonella agona infections, according to Carl Langkop, an epidemiologist who is chief of the Communicable Diseases Control Branch of the Illinois Department of Public Health.

Because Salmonella agona is so unusual, doctors suspect that the cases are from a single source, but have not yet tracked that down. The bacterium is found in chicken, turkeys, cattle and pigs.

Dr. Laurence Slutsker, a medical epidemiologist with the CDC, said that there are no reports of deaths from the illness.

The cases started in early April, and Illinois received reports of four new illnesses Thursday, Langkop said.

Investigation centered in Illinois

Researchers at the CDC work to identify salmonella

Like other salmonella infections, agona usually causes a weeklong illness. Symptoms include vomiting, fever, diarrhea, and abdominal cramps. Infections can be fatal among infants, the elderly and people with compromised immune systems.

The investigation is centered in Illinois, where there are more cases than any other state. In a normal year, Illinois records about 40 cases of Salmonella agona illnesses; in the last seven weeks alone, 34 cases have been confirmed.

Cases also have been recorded in Ohio, Indiana, Missouri, Michigan, New York and Pennsylvania.

The CDC is now launching a new system that can track such outbreaks in the future. The system lets epidemiologists track the DNA fingerprints of individual strains of salmonella.

But right now, the CDC does not know what is causing the current outbreak.