An epidemic is moving across the United States. It has invaded 35 states and sickened 324 people, including 88 children. It has put 66 people into hospitals, and one of the sick people has died. And the Centers for Disease Control and Prevention, responding as it always does to outbreaks that menace Americans, is struggling with how to stop its advance—because the things causing the epidemic are widely distributed across the country, come from many places, and are hard to trace back to their source.

And also, are super-cute. The cause is backyard chickens.

Since January, and continuing into June, there have been seven separate outbreaks of Salmonella—each caused by a different strain of the bacterium and each stretching over multiple states, from 16 down to seven—that have been proved to originate in live chicks and ducklings bought by mail or in feed stores and kept at home or at a school.

Baby chicks and ducklings and the birds they grow into may not sound like much of a threat. But in addition to the 324 cases they have caused this year (so far; the CDC plans to update the case count in the next two weeks), backyard poultry caused 252 cases of illness last year, 363 cases in 2014, 514 cases in 2013 (including 356 cases caused by one Salmonella strain); and 334 in 2012. That is 1,757 cases in 5 years.

If that doesn’t seem like much, consider that 2013-14 saw the largest recent outbreak of Salmonella caused by raw poultry, traced back to chicken produced by the California company Foster Farms. That outbreak generated an enormous public health response, months of media coverage, and lawsuits. It caused 634 known cases. Over the same time period, backyard poultry sickened 877. Yet those illnesses seem to still be flying (sorry) under the radar.

“If you ask someone, ‘Can you get Salmonella from eating undercooked poultry?’ they are absolutely going to say Yes,” Megin Nichols, a public health veterinarian in the CDC’s foodborne outbreak response and prevention branch, told me. “But if you ask them, ‘Can you get Salmonella from touching your backyard chicken?’ they don’t necessarily know that.”

View Images How Salmonella outbreaks linked to backyard chicken have risen since the 1990s, based on CDC data. Original from Behravesh et al., Clinical Infectious Diseases, May 2014

Some of that disconnect may be cognitive dissonance. People buy backyard chickens to opt out of an industrial food system they perceive as unhealthy—so it takes some mental gymnastics to confront that the birds providing homegrown eggs (and sometimes meat) might be hazardous too. But, Nichols said, it might also be lack of awareness—that Salmonella, which resides in chickens’ guts even when birds look healthy, and exits their bodies in their droppings, can spread all over them as they perch and take dust baths and preen.

“On their feet, on their feathers, on their beaks,” Nichols said. “And in the areas where they live and roam. So people are exposed when they clean the coop or otherwise maintain the poultry environment. But we also see people, especially young children, cuddling and snuggling them and kissing them.”

Finally, add in that most people don’t know Salmonella, along with other foodborne illnesses, doesn’t only cause a few days or weeks of lying flat and sticking close to the bathroom. An increasingly solid body of research links it to lifelong illnesses from arthritis to digestive problems to circulatory damage that leads to high blood pressure, kidney failure and stroke.

Casey Barton Behravesh, a veterinarian with a public health doctorate who directs the CDC’s “One Health” office, said this is a new problem. Exposure to live poultry used to be rare, and pretty predictable: It occurred when children were given fuzzy newborn chicks in Easter baskets. “Then in the early 2000s, we noticed a growing trend of more and more outbreaks occurring, not linked to little chicks and ducklings, and not among kids getting sick,” she told me. “It was adults getting sick, people who reported having backyard flocks, which was something we had never seen before.”

View Images Educational material on backyard-poultry disease outbreaks. Image courtesy the CDC; original here.

People are being made ill because they don’t recognize they are at risk—but the structure of the industry, and the systems set up to monitor it, aren’t helping. The federal program that surveys diseases in live chickens, the USDA’s National Poultry Improvement Plan (NPIP) was set up to protect chicken health, not human health. So it tracks Salmonella strains that make chickens sick, but not the ones that cause human outbreaks, and until recently, it focused on the vast commercial poultry trade where those strains would cause costly damage.

Denise Brinson, a veterinarian who is the NPIP’s director, told me that because of the backyard-associated outbreaks, the agency has worked with the CDC to create a program addressing small suppliers. In 2014, it began allowing hatcheries that supply the backyard trade—which sell birds to feed stores and hardware stores, as well as direct to consumers—to join a testing program scaled to the size of their businesses and to advertise that they have NPIP certification.

But to look for that, would-be poultry buyers have to know where the birds are coming from, and that turns out to be more difficult than it should be. Federal investigators including Behravesh documented in 2012 and 2014 that the process of getting chickens to market isn’t a supply chain, it’s a tangle. Birds come from 20 different hatcheries in the US, but many of those hatcheries have contract farmers doing the daily work, and then combine those clutches to make up the millions of birds they ship each year. Because some hatcheries specialize in only certain breeds, they also may “drop-ship”—buy and ship birds from other hatcheries—to make up orders as well.

And at the sales end, birds from different farms and hatcheries may be commingled in the same store pen—increasing the possibility that Salmonella can spread among them, and making traceback to the birds’ origin an extraordinarily difficult task.

All of which means the onus is on individuals to protect themselves: owners of live poultry in backyard or schools, people who visit those owners, even people who handle baby chicks in the stores where they are sold. The CDC’s advice is to keep separate clothes and shoes to wear for feeding birds and cleaning their coops; make sure anyone who touches the birds or their area washes their hands right away; and remember that, no matter how adorable they are, backyard poultry are a food source, not a pet. Despite the temptation, they shouldn’t be smooched or snuggled—especially not by young children, whose immature immune systems put them at greater risk of infection.