At least 90 people in 19 states and the District of Columbia have fallen ill due to an outbreak of salmonella that may be linked to sushi, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) revealed this week. So far, seven people have been hospitalized.

According to the Associated Press, the salmonella outbreak was announced in an internal FDA memo that was not made available to the public. The agency's investigators have focused their work on six "clusters" of restaurants in Texas, Wisconsin, Maryland, Rhode Island and Connecticut, although a spokesperson declined to elaborate on details.

FDA spokesperson Curtis Allen said the illnesses has been caused by the Salmonella bareilly strain, which is far less common and has in the past been associated with sprouts.

According to the CDC, many of the people who reported salmonella symptoms — which can include diarrhea, fever and abdominal cramps — said they had eaten sushi, sashimi or similar foods between Jan. 28 and April 2. The FDA and the CDC are currently looking for additional victims while they investigate the outbreak with local public health officials.

The FDA memo reportedly blames spicy tuna rolls, which the memo called "highly suspect." But the FDA's Allen told the media, "It is too early to speculate on the cause of the outbreak."

Salmonella symptoms can be especially severe and even life-threatening in children, the elderly and people with weakened immune systems.

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Sushi scare: FDA and CDC investigate salmonella outbreak in 19 states
At least 90 people have fallen ill so far.