As the number of confirmed cases of listeriosis reached 84 people in 19 states, including 15 deaths, natural-food types are blaming animal agriculture, others say a single food inspection agency would have prevented the outbreak, the government is telling people to wash their hands, and a group in Denver is using the tragedy to lobby for more paid sick days.

It’s tired but true that major outbreaks of foodborne illness are reproessed through the political filters of punditry to advance a cause, rather than focus on the biological aspects of an outbreak – especially when the unknowns are numerous.

Eric Jensen, the farmers at the center of the outbreak, has no idea how his cantaloupes became infected, and neither do the Food and Drug Administration investigators who have intermittently been in Holly, Colorado, a town of 800 people near the Kansas border.

Regardless of how it happened, the situation has left the town and farm reeling and in fear. Jensen had to quit growing and shipping cantaloupes after the outbreak was discovered — a staggering blow to a region where cantaloupe has always been a proud local tradition.

Sherri McGarry, a senior adviser in the FDA’s Office of Foods, said the agency is looking at the farm’s water supply and the possibility that animals wandered into Jensen Farms’ fields, among other things, in trying to figure out how the cantaloupes became contaminated. Listeria bacteria grow in moist, muddy conditions and are often carried by animals.

The water supply for farms in the Holly area comes from wells and irrigation ditches that tap the nearby Arkansas River. There’s no shortage of thoughts around town about the potential causes.

Proponents for Denver’s Initiative 300 that would let private employees and city workers earn up to 72 hours of paid sick days a year sent out a campaign flier that connects the ballot measure to the deadly listeria outbreak, upsetting opponents.

The mailer by Campaign for a Healthy Denver features a photo of cantaloupe next to a dish of bow-tie pasta with the question: “What can you do to make your food safer? Make sure workers handling food are healthy.”

The mailer continues: “There are many types of food contamination we can’t control. But we can help stop sick workers from handling our food by voting yes on Initiative 300.”

Greg Sauber, co-owner of the Wash Park Grille, said, “It is outrageous and disgusting to use a tragedy for a political campaign. I don’t know where they are coming from with this.”

The U.S. Centers for Disease Control published an outbreak investigative summary yesterday, including a description of how once cantaloupe was implicated, PulseNet, the national molecular subtyping network for foodborne bacterial disease surveillance, detected a multistate cluster with a fourth PFGE pattern combination; a sample of cantaloupe collected from the implicated farm yielded L. monocytogenes with this pattern, and interviews with patients revealed that most had consumed cantaloupe. Isolates with this pattern were then also considered to be among the outbreak strains.

This outbreak has several unusual features. First, this is the first listeriosis outbreak associated with melon. Second, four widely differing PFGE pattern combinations and two serotypes (1/2a and 1/2b) have been associated with the outbreak. Third, this outbreak is unusually large; only two U.S. listeriosis outbreaks, one associated with frankfurters (108 cases) and one with Mexican-style cheese (142), have had more cases. Additional cases likely will be reported because of the long incubation period (usually 1–3 weeks, range: 3–70 days) and the time needed for diagnosis and confirmation. Fourth, this outbreak has the highest number of deaths of any U.S. foodborne outbreak since a listeriosis outbreak in 1998.