Researchers urge the public not to eat or purchase any romaine lettuce until the source of the outbreak can be found.
In an outbreak spanning 16 states as of Sunday, April 22, 53 individuals have contracted Escherichia coli (E. coli) from romaine lettuce.
Since the Centers for Disease Control and Prevention (CDC) is still working to identify a common source, whether it be a grower, supplier, distributor or brand, it recommends throwing out any romaine lettuce at home and avoiding it in restaurants.
Although the lettuce has been linked to the Yuma, Ariz. region, it is often difficult to verify growing areas from labels, and consumers are warned to discard any produce they are unsure about.
The original alerts of lettuce poisoning involved only chopped romaine lettuce and salad mixes, but the CDC has expanded its warning to all types of romaine lettuce, including whole heads and hearts.
The particular serotype of E. coli involved in the outbreak is O157:H7. While most E. coli strains are harmless, O157:H7 produces Shiga toxins, which inhibit protein synthesis in cells.
This particular serotype of E. coli is also associated with hemolytic uremic syndrome (HUS), a serious condition that involves red blood cell destruction which can lead to kidney failure.
Of the 53 individuals affected by the current outbreak, 31 were hospitalized, five of whom were suffering from kidney failure.
There have been no reported deaths to date but due to anticipated delays in reporting, the CDC notes that cases occurring after March 27 may not yet be officially included in reports.
Infected individuals usually begin experiencing symptoms two to eight days after original exposure, with the average being three to four days. Symptoms can include bloody diarrhea, stomach cramps, vomiting and fever, and individuals usually recover within a week.
Those who develop HUS usually do so about seven days after the first appearance of symptoms.
Signs of HUS include infrequent urination, fatigue and paleness.
Furthermore, children, the elderly and immunocompromised individuals are most at risk of being infected and developing HUS.
The CDC advises individuals who have symptoms to talk to a doctor immediately and to record what they remember eating in the week before symptoms appeared. E. coli can be tested for with a stool sample.
Generally, good hygiene such as hand washing, avoiding cross-contamination in the kitchen and cooking meat thoroughly can help prevent contracting an E. coli infection.
Thoroughly washing fruits and vegetables is also recommended; however, in this outbreak, washing romaine lettuce will not remove the E. coli bacteria, as it can remain inside the leaf.