(Des Moines) -- Cases of infections caused by Campylobacter bacteria continue to rise in Iowa.

The Iowa Department of Public Health reports annual cases of Campylobacter infections first topped 1,000 in 2016. With more than 600 cases reported in the first half of this year, the trend continues for the foodborne illness. Barb Fuller is a human sciences specialist with Iowa State University Extension and Outreach. She says is most commonly associated with chicken.

"The biggest cause is eating raw or under-cooked poultry or things that are contaminated by raw poultry -- so if you didn't wash your cutting board or change your plate when you take something out to the grill," said Fuller. "It can also come from things like raw milk or unpasteurized milk, but chicken is the biggest cause."

The Campylobacter bacteria is present in the intestines, liver and giblets of poultry and can be transferred to other parts of the animal when it's slaughtered. Fuller says the bacteria is common, but can be eliminated with proper cooking.

"Probably about 33 percent of chicken that you buy in the grocery store is contaminated with bacteria," said Fuller. "You can't see it, can't smell it or can't taste it, so sometimes we think about chicken with salmonella, but Campylobacter is a big problem."

Symptoms can be severe in people with weakened immune systems, but most people develop a mild reaction to the infection.

"It does cause diarrhea, fever, abdominal cramps and maybe nausea or vomiting," said Fuller. "It causes those general sort of things you might think of when you ate something. It takes about two-to-five days and the symptoms last about a week."

Fuller says person-to-person transfer of the bacteria is possible.

"Usually, you can recover within a week," said Fuller. "You can still be contagious for several weeks, so you need to be careful being around other people -- especially those that may be at higher risk for a foodborne illness. As you're preparing food, make sure you always wash your hands."

Nationally, the Centers for Disease Control and Prevention estimates there are 1.3 million cases of Campylobacter infection annually. More information is available from