Dr. Robert Tauxe, the deputy director of the foodborne, waterborne and environmental disease division at the CDC, says that children, the elderly and pregnant women are most at risk. And no one is immune.

"Healthy people of any age can get very sick, or even possibly die, if they drink contaminated raw milk," he says.

But warnings from federal health regulators haven't dissuaded those determined to drink it.

Bob Ehart, senior policy and science adviser at the National Association of State Departments of Agriculture (NASDA), has been tracking raw milk policy in all 50 states for the past decade. He says more and more states are legalizing its sale.

According to NASDA's most recent survey, conducted in 2011, raw milk sales are legal in 30 states, with a variety of restrictions on how it can be sold. Twelve, including California, Pennsylvania and Utah, allow raw milk sales in retail stores. In Missouri, Kansas and Nebraska, customers have to go to the farm to buy it. And in Colorado, consumers enter into a legal contract with the farmer in what's called a cow-share — a CSA-style operation in which consumers buy a share of a cow in exchange for raw milk.

The CDC has been monitoring this move towards broader legalization and recently reported a corresponding increase in the number of illnesses attributed to raw milk: up four fold from years past. From 2007 to 2012, there were 81 outbreaks reported — an average of 13 per year that led to nearly 1,000 illnesses and 73 hospitalizations. That's compared to just three outbreaks a year, on average, from 1993 to 2006.

The greatest jump was in outbreaks of severe diarrhea, often the result of drinking raw milk tainted with campylobacter-infected feces. Tauxe says that spike should serve as a reminder that no amount of regulation can make raw milk safe.

But NASDA's Ehart suggests some states may not be legalizing raw milk sales to condone it. Rather, he says legalization may give public health agencies the power to regulate a market that might otherwise exist underground.

"Some would say that it would be worse if there's nothing on the books that allows the agency to do anything," Ehart says. "This at least allows them to do something if there's an exposure level that affects public health."

The battle over raw milk regulation is raging in Illinois. Despite being illegal, raw milk sales in the state have grown. Dozens of dairies now supply nearly a half-million customers.

Joe Zanger's three Guernsey cows produce up to 30 gallons of raw milk a day. For the past few years, he's been selling the unpasteurized stuff by the gallon, in glass jars, to a growing number of customers living in Quincy, Ill., the city down the road from his dairy.

Joe Zanger and his son, Abram, clean out the cow barn. For the past few years, Zanger has been selling raw milk by the gallon to a growing number of customers living in Quincy, Ill., the city down the road from his dairy. Photo: Abby Wendle/Harvest Public Media

Zanger says he earns a few hundred dollars a week from this side business — enough to pay for animal feed, vet bills and milking barn maintenance. He believes that one day, it could turn into a profitable venture.

"This is something that I can maybe grow a little bit, if I pick up more customers and buy more cows and just keep recycling that money" into the business, he says.

When Illinois became aware of the growing market, the health department proposed rules that would technically legalize raw milk, but impose strict regulations on the industry. Similar to other states in the region, sales would be limited to the farm.

Farmers would also be required to place a warning label on the product, sell it within five days of milking, and keep records of whom they sell to. By keeping track of where raw milk flows, public health officials say they'll be able to more effectively respond to outbreaks, if they happen. But farmers complain it's an unnecessary headache.

When it comes to the milking operation, the proposed rules mandate that all farmers keep their dairy cows "free from dirt" and routinely have their milk tested for harmful bacteria. Farmers would also have to upgrade their infrastructure to have an easily cleanable milking barn, proper plumbing, and a separate milk house to store the product in a refrigerated, stainless-steel tank.

The Illinois proposal is currently on indefinite hold. Legislation to open the market in both Iowa and Indiana was proposed in 2013, but stalled in committee.

The proposed regulations in Illinois have garnered fierce resistance from raw milk consumers and producers, who see them as an attack on small businesses and personal freedom.

"The free market has taken us so far already. Why not just keep letting it go?" asks dairyman Zanger. "If you come out to my farm and you see something you don't like that makes you not want to buy my milk, you have every right to say, 'No, thanks.' If everything looks appropriate, why can't you buy it?"

In the absence of legislation in Illinois, producers like Zanger are left wondering whether they'll have to pay for expensive upgrades in the near future — or worse, be shut down by regulators.

For now, Zanger continues to sell raw milk and cream to his customers. Even though it's illegal, the thirst is there, and Zanger says so is his commitment to quenching it.

Abby Wendle is a reporter for Tri States Public Radio. A version of this story appeared on the site of Harvest Public Media, a public radio reporting collaboration that focuses on agriculture and food production.

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