Consumers should avoid eating raw alfalfa sprouts until further notice, according to a warning issued jointly by the Food and Drug Administration and the Centers for Disease Control. The sprouts have been linked to salmonella cases in several states and officials believe that tainted seeds, sold nationwide, may be the cause of the outbreak. Other types of sprouts have not been implicated.

There have been 31 cases of salmonella saintpaul in Michigan, Minnesota, Pennsylvania, South Dakota, Utah and West Virginia linked to alfalfa sprouts since mid-March, the FDA said. No deaths have been reported. The current outbreak appears to be an extension of an outbreak that sickened more than 100 people in February and March in Nebraska, South Dakota, Iowa, Kansas, and Minnesota, officials said.

Some of those sickened reported eating raw sprouts at restaurants; others reported purchasing the raw sprouts at the retail level, the FDA said. The results of an initial investigation trace the contaminated raw alfalfa sprouts to multiple sprout growers in multiple states.

There have been a number of foodborne illness outbreaks linked to alfalfa sprouts over the past two decades. In 1999, the FDA issued guidance to growers that recommended disinfecting the seeds immediately before the start of sprouting and regularly testing the water used for every batch of sprouts for salmonella and E coli O157:H7 contamination.

The CDC and FDA recommend that persons at high risk for complications, such as the elderly, young children, and those with compromised immune systems, not eat raw sprouts because of the risk of contamination with salmonella or other bacteria. For others, the FDA offers this advice:

• Cook all sprouts thoroughly before eating to significantly reduce the risk of illness.
• Sandwiches and salads purchased at restaurants and delicatessens often contain raw sprouts. Consumers who wish to reduce their risk of foodborne illness should specifically request that raw sprouts not be added to their food.
• Homegrown sprouts also present a health risk if eaten raw or lightly cooked. Many outbreaks have been attributed to contaminated seeds. If pathogenic bacteria are present in or on the seeds, they can grow to high levels during sprouting even under clean conditions.