A major outbreak of botulism, a rare type of food poisoning, struck 10 people in Northern California over the last month, killing one Antioch man. Sacramento County health officials traced the illness to a gas station in Walnut Grove, where the victims were sickened after eating nacho cheese sauce from a dispenser.
Botulism is caused by a dangerous nerve toxin created when a bacteria called clostridium botulinum multiplies in food. Symptoms begin with vomiting and blurred vision followed by a slow paralysis that can lead to respiratory failure if an antitoxin is not administered in time.
While the exact cause of the recent contamination is unknown, health officials believe it is isolated to the Valley Oak Food and Fuel gas station and did not involve Gehl Foods, the Wisconsin-based manufacturer of the cheese sauce. The station stopped selling the sauce May 5. Health officials say there’s no ongoing risk to the public.
Outbreaks of botulism through the sale of packaged foods are especially rare, said Linda Harris, a food safety microbiologist at UC Davis and an expert in foodborne pathogens. Only 15 cases of foodborne botulism were reported in the United States in 2014, according to the most recent data from the U.S. Centers for Disease Control and Prevention.
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Harris explains the risk and how to protect yourself at home and while eating out.
Q. Where have we historically seen botulism in the U.S.?
A. It’s usually from one of two main things – either it’s improperly home-canned foods or improperly fermented seafood products. Typically you’re going to see those in Alaska or Washington state, where there are traditional First Nations or native foods. You’ll see things like seal blubber or fermented trout – things that are unusual to many of us.
Q. Why are canned foods specifically an issue?
A. Clostridium botulinum has some unique characteristics. It doesn’t like oxygen. If you heat that jar up, the product expands and so you push the oxygen and the air out. As it cools, that creates the vacuum and gets a seal on the lid, and you create this nice, oxygen-free environment in the jar.
Another thing botulinum absolutely needs to multiply is nutrients and a nonacidic environment. Things like fruit, those are very acidic and so clostridium botulinum cannot deal with the acid that’s in those products naturally. Where we see problems with home-canned foods is typically with vegetables or things that have meat in them, because those are not acidic.
Q. What do you need to do home canning right?
A. Get the acid right, if you’re going to control by acid. But if you want to can meat or soup or some kind of vegetable, follow the right recipe that gives you the proper time to can the product under pressure. There are specific ways in which to operate a pressure canner. If you follow the recipe and you operate your canner correctly, those foods are not a problem.
Q. What about commercial canning?
A. We have very strict regulations for canned foods in the U.S. We’ve had regulations that date back 100 years. In California, a lot of the research and foundation of science behind canning actually happened here because in the early 1900s California was canning a lot.
That’s how we were able to sell across the country. We had outbreaks from California canned spinach and olives, and they caused a lot of problems for the industry.
Q. Are canned items at farm stands dangerous?
A. If it’s a jam or if it’s canned fruit, those are very low risk and they’re not covered by the same regulations. But if you go to a fruit stand and someone is selling pickled asparagus or pickled cucumbers, you’d want to make sure they actually know what they’re doing and that they have a canning license.
Q. Aside from canning, what else could be a botulism risk when cooking at home?
A. It’s hard to say how risky, but there is a reason we tell people, for all kinds of food-safety reasons – not just botulism – that you should limit the amount of time food is at room temperature after it’s prepared. We have a two-hour guideline before getting stuff into the fridge.
There was once an issue with aluminum foil-wrapped potatoes that were roasted in an oven and then left out. In that case you’ve killed off all the bacteria except clostridium botulinum, and right at the interface between the foil and the skin of the potato you’ve driven away all the oxygen. There’s moisture and temperature, and nutrients leaking out of the potato. It’s a nice environment. If you leave it out for long enough, botulinum can produce its toxin.
Q. How can you prevent botulism when you’re buying food?
A. When I’m buying at a restaurant or a place where food is being prepared, if there’s prepared food sitting out, I look at the overall sanitation of the facility. I have walked out of restaurants because the bathroom is a nightmare. If the bathroom is a nightmare, what’s the kitchen like?
I look for visual clues on how much attention they’re paying to sanitation and how they’re storing the product.
With gas stations, if you have a vendor that’s going through hundreds of servings of this cheese sauce a day, it won’t be sitting out for a long time. But in a low-volume place, that could be part of it. They had to have the contamination of the bag, the wrong temperature, and too much time. The instructions are to hold that cheese about 140 degrees, and that should have been protective. Multiple things went wrong (at Valley Oak Food and Fuel). When you have outbreaks, often it’s multiple things.
Q. How worried should the public be about botulism?
A. Of all the types of foodborne illness, the numbers we have on botulinum are pretty solid. It’s a very, very small number of cases a year. And it’s not from commercial foods, for the most part.
People need to be smart about food safety in general … following basic sanitation and cooking things properly, keeping hot things hot and cold things cold, those things will really protect you from foodborne illness in general.