In late October, Frank Yiannas, Deputy Commissioner for Food Policy and Response at the Food and Drug Administration, announced that investigations were in progress concerning two outbreaks of Shiga toxin-producing E.coli O157:H7 infection.  At the time Yiannas did not identify a vehicle of infection, but his Agency was cooperating with CDC and local health departments.  In the interim the Department of Agriculture and Rural Development in Michigan is advising consumers not to eat Tanimura & Antle brand romaine lettuce packed in Salinas in mid-October. 

Outbreaks of STEC infection have occurred in successive recent years attributed to consumption of contaminated romaine lettuce and other leafy greens grown in the Yuma Valley of Arizona and the Imperial Valley in California.

Concentrated animal feeding operations (CAFOs) are considered to be responsible for contaminated runoff introducing STEC into irrigation water.

Following applied research, some measures have been taken to reduce the possibility of infection of consumers of green produce but the measures taken are probably more ameliorative than specific.  The leafy greens industry needs an absolute kill step between production and packing to ensure the wholesomeness of their products.