Health officials are warning consumers not to eat certain brands of alfalfa sprouts that have been linked to an unusual outbreak involving different disease-causing bacteria.

At least 55 people have become ill with either E. coli or salmonella infections in 15 states, the Centers for Disease Control and Prevention reported Friday. Two people got sick with both germs. Four have been hospitalized. No deaths have been reported.

The illnesses are being linked to alfalfa sprouts produced by Everything Sprouts, a Minnesota grower, and sold under the Calco and Everything Sprouts brands to restaurants and grocery stores. Everything Sprouts said Friday it is recalling certain lots of the alfalfa sprouts in 5-ounce containers with a lid that have been delivered since May 27.

Most of the cases are in Minnesota and Wisconsin. Minnesota health officials said 23 people in the state became ill between July 8 and Aug. 8 and two have been hospitalized. In Minnesota, three had salmonella, and one of them also had a strain of E. coli bacteria called STEC O168:H8. Seven other people were sickened with a different version of E. coli, called STEC O103:H25. Thirteen more had yet another strain, STEC O26:H11.

Wisconsin investigators have identified another 18 cases of illness tied to alfalfa sprouts, Minnesota officials said.

The number of illnesses will likely increase.

Federal and state officials are working together to pinpoint the source and scope of contamination.

Food poisoning outbreaks tend to be defined by one type of germ. In 2019, the CDC reported a multistate outbreak of gastrointestinal illnesses linked to oysters that included E. coli, campylobacter, norovirus and other pathogens.

“It’s very unusual to have two bugs,” said Bill Marler, a Seattle lawyer who has worked on food safety cases for decades.

It’s not surprising that alfalfa sprouts might be the culprit, he added. It’s easy for the seeds to harbor contaminants, it’s difficult to clean them, and it’s easy for contaminants to spread when they are grown in warm water, Marler said.

Shiga toxin-producing E. coli — or STEC — can cause stomach cramps and bloody diarrhea. Infections can lead to hemolytic uremic syndrome, a severe complication that involves acute kidney failure and other severe problems.

Salmonella poisoning can cause diarrhea, fever, severe vomiting, dehydration and stomach cramps.

The CDC urged consumers to throw away or return the affected sprouts and to wash items and surfaces that may have touched them.