Mea Andrews, a reporter for the Missoulian, recapped an E. coli O157:H7 outbreak that occurred in Missoula, Montana, in 1995 in a recent article.
The culprit was never fully pinned down, but it was most likely leaf lettuce. In fact, the Missoula cases were believed to be the first reported community outbreak of E. coli 0157:H7 associated with eating lettuce, according to a wrap-up article in The Journal of Infectious Diseases in 1998.
Two possible sources came to the forefront: Several lettuce farms in Washington state that were located near each other, or a local lettuce-growing operation that supplied Missoula-area restaurants and stores.
Most likely, the lettuce from the Montana farm, never identified, was the source of the outbreak. How the lettuce was contaminated also was never established. Four possibilities were discussed:
- Improperly composted manure from a local dairy;
- Cattle feces from a nearby, uphill farm infecting runoff or irrigation water;
- Cattle feces infecting stream water;
- Infection from other animals that were present, including sheep or deer.