Some 388 people have been sickened in a new, nationwide outbreak of the bacterial illness salmonella. The source of the infection, which is typically spread through consumption of contaminated food, is unknown.

The Centers for Disease Control and Prevention (CDC) is investigating the outbreak, which has hit 42 states since September. Ohio has reported more than 50 cases of salmonella since October, the Associated Press reports.

This strain of the illness, Salmonella typhimurium, usually comes from poultry, cheese and eggs, and the CDC is advising people not to eat raw or undercooked meat or un-pasteurized dairy products, to scrub their hands after touching raw meat and to thoroughly wash any produce.

Still, the agency’s disease trackers, who were criticized for taking three months to trace another large salmonella outbreak last spring to Mexican Serrano peppers, haven’t determined the latest outbreak’s origin. They mistakenly blamed tomatoes for last year’s scourge, costing growers $100 million in sales.

Salmonella causes diarrhea, fever, and abdominal cramps that can last four to seven days. While most people recover on their own, some require hospitalization, as have 18 percent of patients in the latest outbreak, CDC officials say. The food poisoning is potentially fatal if the bacteria spreads from the intestines to the blood and other organ systems. The elderly, infants and people with weakened immune systems are most vulnerable to a severe illness, which can usually be treated with antibiotics.

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