The number of confirmed cases of listeriosis tied to contaminated cantaloupes has edged up to 123, according to the CDC.
Pennsylvania reported its first case since the agency's last update, becoming the 26th state involved in the outbreak. Two deaths -- one each in Colorado and New York -- have been added to the toll, bringing the total to 25, not including one miscarriage.
All of the people who died after becoming infected with one of the four outbreak-related strains of Listeria monocytogenes ranged in age from 48 to 96 (median 87), although illnesses have been reported across age groups.
The CDC continues to recommend not eating Rocky Ford-brand cantaloupes from Jensen Farms in Colorado, which have been identified as the source of the outbreak. That is especially important for adults 60 and older, people with weakened immune systems, pregnant women, and newborns -- groups that are most at risk of developing listeriosis.
All other cantaloupes with a known source that are on the market are safe to eat, the agency said, adding that if the source is unknown, the fruit should be thrown out.
Jensen Farms issued a recall on Sept. 14 and, because cantaloupes have a shelf life of about two weeks, the affected fruit should no longer be on store shelves. But it is possible that some contaminated cantaloupes remain in people's homes, as Listeria can grow both at room temperature and at refrigerator temperatures.
The CDC noted that it is possible that illnesses will continue to be reported because listeriosis can occur up to two months after ingesting the pathogen, although it appears that the number of cases peaked near the end of August or the beginning of September.
Coinciding with the CDC's update, the FDA released results from its investigation into the exact cause of the contamination at the Jensen Farms facility.
An environmental assessment revealed a range of possible explanations for the introduction, spread, and growth of Listeria at the farm.
It is possible, the FDA said, that the bacteria could have been present in the field where the cantaloupes were grown or that a truck used to transport culled cantaloupe to a cattle operation could have introduced the contamination.
The agency pointed to the design of the packing facility to explain how the bacteria spread. As constructed, the design allowed water to pool on the floor near the equipment and employee walkways and made the floor difficult to clean. In addition, the packing equipment could not be easily cleaned, and the washing and drying equipment was previously used for another raw agricultural product.
A final possible explanation for the growth of Listeria on cantaloupe -- which has not been reported before the current outbreak -- is the lack of a step to pre-cool the cantaloupes after harvesting and before placing in cold storage. Resulting condensation could have encouraged growth, the FDA concluded.
The agency said the investigation is still considered open.
The same pathogen is also responsible for recalls of bagged lettuce by two different producers, one in California and one in Pittsburgh, although no adverse events related to the lettuce have been reported.