"Will that kill my kid?" Salmonella edition

Mmmm...raw eggs... PC: Pam Menegakis ON Unsplash

Mmmm...raw eggs...

PC: Pam Menegakis ON Unsplash

When I was growing up, baking came with a "one finger" rule. The rule was partly practical: four kids could demolish a bowl of batter pretty quickly, so the one finger rule meant that some batter was always left for baking. But the rule was also a risk assessment: one finger's worth of batter meant getting a tiny fraction of any raw eggs inside, and, therefore, limited exposure to salmonella.

Throughout my adult life I've tried to live by my parents' example. But I've shown no restraint when it comes to cookie dough. I'm way past the one-finger rule. Sometimes I eat by the tablespoon. Sometimes I eat perfectly-formed balls of dough straight from the cookie scooper. 

No matter the recipe, it always ends the same way. A few hours later I'm feeling guilty about my recklessness and monitoring bowel movements for signs of my impending demise. A few days later I've suffered no consequences. A few weeks later I'm back to slurping cake batter from a measuring cup.

So how unsafe have I been, really? Was I ever actually taking my life into my hands, even in my most impulsive dough-eating moments?  How prevalent is salmonella? And when salmonella occurs, how dangerous is it? 

What is salmonella? 

The CDC estimates that there are over one million food-borne cases of salmonella each year. Salmonella infections generally clear up on their own within a week, though some patients may need to be hospitalized for dehydration. 

Salmonella is very unlikely to kill you. But it won't be like having a cold, when it's all chicken soup and snuggling on your couch watching Netflix. With salmonella, you'll want the Netflix app for your phone, because you'll be spending much of the next few days in the bathroom. Salmonella is one of the many causes of gastroenteritis (which we often euphemistically refer to as either stomach flu or food poisoning). Salmonella bacteria hangs out in the stomach and intestines, causing nausea, vomiting, diarrhea...basically, all the symptoms that will make you swear off raw dough for a while. 

How many times can you lick the bowl?

One reason that we're more likely to fear salmonella in our cookie dough is that it when we were kids, salmonella was all over the news. Between January 1985 and May 1987, there were sixty-five Salmonella outbreaks in the Northeastern U.S. Some of those outbreaks were massive, such as the Hillfarm dairy 2% milk that was linked to more than 16,000 cases and estimated to have effected nearly ten times that number of people. Many of the salmonella cases were linked to eggs. In 1988, an article in JAMA traced 77% of salmonella cases reported in the Northeastern U.S. to Grade A eggs. The salmonella outbreaks of the 1980s were serious and systemic. But given stricter safety policies for food producers, what are the risks of salmonella contamination now? 

Unrepentant spoon-licker L.V. Anderson did the math on her own raw egg consumption. She has baked (and licked) an average of once per month since age 12, which means she has consumed 360 uncooked eggs. The rate of salmonella contamination is about 1 in 20,000 eggs. Assuming that rate was true for all of Anderson's egg-consuming years, for each raw egg eaten she had a 19,999/20,000 chance of the egg NOT being contaminated with salmonella. Multiplied over those 360 eggs, she had a 98.2% chance of not getting any salmonella-infected eggs. 

But her chances of avoiding salmonella infection were probably even higher than that, given a few facts about salmonella. Salmonella will not grow in cold conditions, so properly refrigerated eggs containing salmonella are likely to have small amounts (which may not be ingested by the bowl licker and cooked off in the oven). Even if ingested, salmonella bacteria don't always lead to infection, because other organisms in the body tend to fight it off.

How many backyard chickens do you have to raise? 

Egg-based salmonella outbreaks still do occur. The most recent egg-based Salmomella outbreak was in 2016, with just 8 cases reported. As a general rule, then, we can all be a little more comfortable licking the spoon. 

But a new source of salmonella infection has been popping up in people's backyards. 

People have been flocking to backyard poultry farming for all sorts of reasons, but one of the most-frequently cited reasons is having healthier eggs.

Unfortunately, at least one study has demonstrated that eggs from backyard birds are more likely to contain salmonella than commercially-produced eggs. And salmonella infections from backyard poultry are on the rise. In 2015, there were 252 cases of salmonella infection from live poultry. In 2016 there were 895. As of September of this year, 1120 people have been infected with salmonella carried by backyard chickens. 

Without accurate figures on backyard chicken coop ownership, it's hard to figure out what the risk of salmonella infection is for any particular chicken owner. One 2010 survey of people in four metro areas put the number of chicken owners as .8 percent of the population, with another 4 percent planning to purchase chickens. 

That data makes the rate of salmonella infection from live poultry look a bit different. 1120 cases seems high, but not when compared to the chicken-owning population. If the rate of chicken ownership has held to .8 percent (2.5 million people), then the rate of salmonella infection among chicken owners would be .04 percent per year in 2017, or 4 in 10,000 people. 

Should you respond to this news by fleeing the coop? No. But if you're looking for better eggs, know that there's at least one eggsellent taste test suggests no taste difference between backyard and commercially-produced eggs. 

How many times do you have to kiss a tiny turtle? 

Many of the chicken coop scare stories in this year's news are about treating chickens as pets. Kissing and cuddling with those chickens does seem like a good way to court salmonella. 

And that's the basic story from another lesser-known salmonella source: reptiles and amphibians. 

If you spent your childhood begging for a pet tiny turtle, chances are you never got one, because they were banned for sale in the U.S. beginning in 1975. 

Tiny turtles aren't considered any more or less dangerous than big turtles, because salmonella is naturally present in the intestinal flora of many reptiles and amphibians. But tiny turtles are more likely to be given as gifts to little kids. And because kids are unreliable handwashers who put everything in their mouths, tiny turtles were leading to lots of salmonella infections.

Even though they have been banned for over four decades, tiny turtles are still reliable spreaders of salmonella infection. In recent years salmonella outbreaks have also been linked to other pets. In 2014 it was bearded dragons. In 2015 it was crested geckos. In 2011 it was water frogs. Although in each outbreak the number of cases is relatively small, amphibian- and reptile-borne salmonella infections tend to be more serious, because of the ages of those handling them. This year, there have been 37 reported salmonella cases linked to pet turtles. 43 percent of those cases led to hospitalization. That rate, which is higher than the hospitalization rate for food-borne and poultry-borne infections, suggests that more vulnerable populations are exposed to them (namely, small children). 

Should you avoid all reptiles and amphibians as pets? The CDC recommends keeping them out of the house until the kids' fifth birthday, which helps ensure proper handling and hygiene. 

So, can you lick the spoon? Hug the chicken? Kiss the turtle? Raw eggs, backyard livestock, and pets are all most likely harmless, and even when harmful, survivable. But waiting to eat the cookies until they're baked, washing your hands before coming inside from the chicken coop, and waiting until age 5 to get a pet snake are all good lessons in patience.