Editor's Note: Updated December 17, 2019, 9:25 am.
US Centers for Disease Control and Prevention (CDC) officials have notified the public of an ongoing investigation regarding a multistate outbreak of Escherichia coli O157:H7 infections likely connected to romaine lettuce. CDC, US Food and Drug Administration (FDA), and state officials are collaborating to identify illnesses and trace the contamination through the transmission chain.
FDA, CDC, and state health authorities believe their traceback evidence indicates that romaine lettuce from the Salinas, California growing region is the likely source of this outbreak. While they have not identified the source publicly, investigators believe they have found a common grower.
As of December 2, 2019, a total of 102 people from 23 states have been reported infected with the outbreak strain.
Onset of illness dates range from September 24 to November 14, 2019. Previous reporting featured an onset range that ended on November 8.
A total of 58 hospitalizations have been reported thus far, with 10 people developing hemolytic uremic syndrome, a type of kidney failure. There have been no deaths reported.
Antibiotics are not recommended for patients with suspected E. coli infections until diagnostic testing can be performed and E. coli infection is ruled out. Some studies have shown that administering antibiotics to patients with E. coli infections might increase their risk of developing HUS, and a benefit of treatment has not been clearly demonstrated.
The investigation includes illnesses recently reported by the Wisconsin Department of Health Services and the Maryland Department of Health. The Maryland Department of Health identified Shiga toxin-producing E coli 0157:H7 in an unopened package of Ready Pac Foods Bistro Chicken Caesar Salad collected from a sick individual in Maryland. Whole genome sequencing is underway to determine whether the sample collected in Maryland is closely related to the E coli found in people affected by the outbreak.
Public health officials are using the PulseNet system to identify further illnesses that may be part of the outbreak. The PulseNet system is a CDC-coordinated national subtyping network of public health and food regulatory agency laboratories. PulseNet maintains a national database of sequences, allowing investigators to compare them to the results of whole genome sequencing and identify cases constituting an outbreak.
Ill individuals are being interviewed by state and local public health officials to determine what they ate in the week before their illnesses began. While ill people in Maryland reported eating the Ready Pac Foods Bistro Chicken Caesar Salad, individuals in other states had not reported eating this particular salad.
As part of the traceback investigation the FDA traced the supply of romaine lettuce in the salad, and has identified romaine lettuce from the Salinas, California growing region as a likely source of the outbreak.
Consumers are advised not to eat romaine lettuce harvested from Salinas, California. Retailers are advised not to serve or sell romaine harvested from the region. Suppliers should not ship or sell romaine harvested in Salinas, California. This applies to all use-by dates and brands of romaine lettuce from the region.
Romaine lettuce harvested outside the Salinas region has not been implicated in the outbreak investigation at this time. Additionally, hydroponically and greenhouse grown romaine, voluntarily labeled as "indoor grown," does not appear to be connected to the current outbreak.
CDC provided demographic details of those affected, detailing that ill people aged 3 to 89 years. The ill individuals have a median age of 25 years. Additionally, 67% of ill individuals are female.
Investigators believe that the Salinas grower identified is the common thread between this outbreak and 2 smaller ones with distinct and separate strains, one taking place in Seattle Evergreens restaurants and the other among consumers who ate Fresh Express Sunflower Crisp Chopped Salad Kits.
A previous outbreak linked to romaine lettuce took place over the summer, and was announced by FDA officials on November 1, 2019 .
For the most recent case counts and to see locations associated with the E coli O157:H7 outbreak under investigation, see the Contagion® Outbreak Monitor.