In all, 42 states have reported nearly 400 cases since November. The Centers for Disease Control and Prevention (CDC) is investigating the outbreak, but no source has been identified, health officials said.
State health department investigators are participating, but no new cases have been reported in Minnesota since Dec. 22.
Of the 30 cases in Minnesota, seven were in the Twin Cities area and the rest were scattered across the northern part of the state; 11 people have been hospitalized. A third of the patients are nursing home residents, but not from the same nursing home, a pattern that investigators find puzzling, said Health Department spokesman Doug Schultz.
The first cases in Minnesota began popping up in November, and the number has steadily increased since then, he said. As the public learns of the outbreak, more cases could be reported.
In Ohio, 51 people in 20 counties had the same type of salmonella, all about the same time that five cases appeared in Georgia. At least a dozen were hospitalized. California officials say they had 51 cases as of last week. Illinois and North Dakota also have confirmed cases.
Most people infected with salmonella develop diarrhea, fever and abdominal cramps 12 to 72 hours after infection. The illness usually lasts four to seven days, and most people recover without treatment.
Steps to protect against the illness include careful handling and thorough cooking of raw meat and frequent hand washing.
CDC officials say the cases in the outbreak have all been genetically fingerprinted as the Typhimurium type, which is among the most common forms of salmonella food poisoning.