Protecting families from contaminated food and water
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Protecting families from contaminated food and water
Posted in Food Safety,Our Blog,Outbreaks & Recalls on October 29, 2025
Foodborne botulism, while rare is serious. Even fatal in some cases.
This summer, the Centers for Disease Control and Prevention’s (CDC) Morbidity and Mortality Weekly Report (MMWR) explored a case study on the topic. Homemade canned nopales at a family gathering sent some family members to the hospital.
This scary, but interesting case study serves many purposes.
In addition to demonstrating how a foodborne investigation progresses, it also sheds light on potential risks associated with home canning. It is a great opportunity to discuss some best practices for this time-honored tradition.
This story of foodborne botulism starts on June 21, 2024 at a family gathering. It was a warm day. During the gathering, the outdoor temperature was over 100° F.
The family had a tasty spread. Pork tamales. Hamburgers. Nopales salad (a type of prickly pear cactus popular in traditional Mexican dishes).
The food was so good, and the company so nice, that another gathering was held the next day and the leftovers were served again. June 22 was also a warm day, with outdoor temperatures again topping 100° F.
The following day, June 23, 2024, people started falling sick.
It started with a 42-year-old woman going to the hospital after feeling dizzy, having a sore throat, and experiencing gastrointestinal symptoms for at least 12 hours. She was diagnosed with heat-related dehydration and was later discharged. She returned the following day (June 24) but left before being evaluated.
Meanwhile, symptoms worsened.
She went back to the hospital the next day (June 25) and was admitted and placed on mechanical ventilation within six hours of arrival. Her symptoms now included persistent dizziness, blurry vision, a drooping eyelid, and difficulty swallowing. While at the hospital, progressively descending paralysis and impending respiratory failure led the hospital to suspect botulism.
Meanwhile, around the time the first patient is being placed on mechanical ventilation and steadily declining, six others who attended the gathering began feeling sick enough to go to the hospital. Some were even at the same hospital as the first patient. Others were at a hospital nearby.
These patients also reported a range of neurologic symptoms from June 23 and June 24.
Since botulism was suspected in these patients and other family members who attended the same events were experiencing similar symptoms consistent with botulism, hospital staff notified the California Poison Control System (CPCS) and the Fresno County Department of Public Health (FCDPH), who contacted the California Department of Public Health (CDPH) to request equine heptavalent botulinum antitoxin (HBAT).
This is the primary treatment for non-infant botulism.
FCDPH initiated an outbreak investigation on June 25, 2025.
At this time, investigators understood that the gatherings held on June 21 and June 22 were likely the sites of exposures and that clinical diagnosis for botulism was made for cases based on history, epidemiologic links, and/or physical examinations.
Laboratory results were not yet available on June 25, 2025.
However, three more people were hospitalized days later (June 27, 2024).
Of the 31 people who attended one or both of the gatherings, 10 reported illness between June 23 and June 27, 2024. Some sought medical attention right away. Others waited up to five days before seeking care.
Of those 10, eight were diagnosed with botulism. All 10 patients were hospitalized. Hospital stays ranged from two to 42 days, with 4 days being the median length of stay.
Two of the patients were ultimately determined to have “anxiety symptoms.”
With so many family members you shared food with dropping like flies and being hospitalized, I can understand the stress.
As part of the outbreak investigation, FCDPH Environmental Health Division investigators inspected the homes of the first patient and the fourth patient. This took place on June 26 and June 27, 2024, respectively.
Investigators recovered refrigerated leftover food items from the gatherings. Food items included hamburger patties, homemade pork tamales, and home-pickled serrano peppers. Fruit salad and nopales salad samples were also recovered from outside trash bins.
The nopales salad was prepared at the fourth patient’s home. Investigators collected 23 food jars (reused commercial food jars with visibly corroded lids) containing either nopales or tomatoes. These jars were stored in a covered structure without air conditioning. They were sent to CDPH Microbial Disease laboratory (MDL) for testing.
According to the fourth patient, the nopales salad was prepared with fresh onions, fresh tomatoes, and home-preserved nopales.
The patient explained that the jars were prepared by immersing them in boiling water, adding chopped, uncooked nopales with a small amount of salt. She then closed the jars with new metal lids. They were then stored for six weeks in an outdoor shed behind her home. The patient indicates that she has been home preserving food for years using this same technique using this method that was taught to her by friends and relatives over the generations. The patient indicated that she was unaware of the risk of botulism associated with this practice.
Fortunately, all patients survived their illnesses.
After finding this case study, I figured it was a great time to talk about foodborne botulism and how to reduce your risk when canning food at home.
Foodborne botulism is caused by the bacteria, Clostridium botulinum. It is a neurotoxigenic species. Meaning, the bacteria produce toxins that impact the brain.
Early diagnosis of foodborne botulism is quite difficult. As in the case of the first patient, symptoms can sometimes resemble dehydration. It isn’t until more serious symptoms present themselves that clinical diagnosis and appropriate laboratory testing take place that diagnoses are made.
Unfortunately, that is when things become more serious and life-threatening.
Symptoms of foodborne botulism begin with mild to serious paralysis. It starts with the head and then moves down to the arms and legs causing weakness or paralysis. Respiratory problems occur when paralysis reaches the diaphragm and intercostal muscle. Patients with these symptoms often need mechanical intubation.
Other symptoms may include:
Prompt treatment results in a more favorable outcome.
Home-canned nopales were determined to be the source of this foodborne botulism outbreak. So, where did patient D (the person who made the home-canned nopales) go wrong?
According to the CDC, “foods that are not properly processed, fermented, preserved, stored, or refrigerated can facilitate C. botulinum growth and toxin production, particularly if the food is in a low-acid, unrefrigerated, and anaerobic environment.”
The patient indicated that she dipped the jars in boiling water. But that is not sufficient to guard against the growth of harmful germs like C. botulinum.
Proper canning of these low-acid foods requires jars to be sterilized both when empty AND after they are filled with food.
How do you do that?
For low-acid foods, a pressure canner is needed. Jars must be immersed in boiling water, immediately filled, and properly sealed using a pressure canner. For non-low-acid foods, a water bath canning method may be sufficient.
However, with low-acid foods, like nopales, a pressure canner is absolutely necessary.
Have you canned food at home before? If so, have you considered all of the safety steps necessary to ensure all of your hard work doesn’t go to waste at best, or make people sick at worst?
If you intend to can food, consider getting information from a trusted source, like the National Cener for Home Food Preservation.
Specific protocols, time and temperature requirements, and other tips can be found on their website. Take the time to research what you want to make. Skipping steps could lead to illness, hospitalization, or worse.
If you’d like to know more about food safety topics in the news, like “Foodborne Botulism: When Nopales Go Bad and Canning Safety” check out the Make Food Safe Blog. We regularly update trending topics, foodborne infections in the news, recalls, and more! Stay tuned for quality information to help keep your family safe, while The Lange Law Firm, PLLC strives to Make Food Safe!
By: Heather Van Tassell (contributing writer, non-lawyer)