PAYSON — Utah County health officials issued a warning Wednesday about the outbreak of a food-borne illness that appears to be linked to a Payson dairy farm.

So far 15 people have tested positive for campylobacteriosis, an infectious disease caused by ingesting bacteria. Officials also say several others have reported symptoms similar to those caused by the bacteria.

The disease is not unusual and is rarely life-threatening, authorities say, but the recent outbreak is much larger than normal. "We basically have seen a fourfold increase" in the number of cases, said Lance Madigan, Utah County Health Department spokesman.

The disease usually causes diarrhea, cramping, abdominal pain and fever within one to 10 days after exposure. Some experience nausea or vomiting, as well.

Doctors are required to report cases to the health department, but the department rarely sees more than three cases per month in the county, Madigan said.

When the department's epidemiologist, Lisa Guerra, heard about three Campylobacter diagnoses in one day, she said she immediately began investigating. Guerra interviewed the patients, who all live in southern Utah County.

"The common element reported by individuals in our investigation is the consumption of raw or unpasteurized cow and/or goat milk from Woolsey's Dairy in Payson," Guerra said.

Nine of the cases were traced back to raw milk purchased from Woolsey's Dairy. Only one person has been hospitalized, and several of the cases occurred within a few families that had several sick members.

Inspectors from the Utah Department of Agriculture and Food visited the dairy farm Wednesday and collected samples to be tested for the bacteria.

"We expect to get the results back by Sunday," said Larry Lewis, public information officer for the department.

Unpasteurized milk products or contaminated water are often to blame in large outbreaks of Campylobacter infections, according to health department officials, and either the animal or the milk-processing equipment can act as a carrier of the bacteria.

"There are some who advocate the use of unpasteurized milk and other products," said Dr. Joseph Miner, health department director, in a statement released Wednesday. "However, consuming unpasteurized products greatly increases the risk of exposure to food-borne infections, including Campylobacter, salmonella, shigella and toxic E. coli."

The department of agriculture has asked the owner of Woolsey's Dairy, 2232 W. SR 198, Payson, to stop selling his unpasteurized products voluntarily until the test results return.

Owner Lars Woolsey said he's leaving the decision to buy up to his customers.